Redesign the landing page, mount public timeline on it (#4122)

* Redesign the landing page, mount public timeline on it

* Adjust the standalone mounted component to the lacking of router

* Adjust auth layout pages to new design

* Fix tests

* Standalone public timeline polling every 5 seconds

* Remove now obsolete translations

* Add responsive design for new landing page

* Address reviews

* Add floating clouds behind frontpage form

* Use access token from public page when available

* Fix mentions and hashtags links, cursor on status content in standalone mode

* Add footer link to source code

* Fix errors on pages that don't embed the component, use classnames

* Fix tests

* Change anonymous autoPlayGif default to false

* When gif autoplay is disabled, hover to play

* Add option to hide the timeline preview

* Slightly improve alt layout

* Add elephant friend to new frontpage

* Display "back to mastodon" in place of "login" when logged in on frontpage

* Change polling time to 3s

68 files changed, 956 insertions, 655 deletions

diff --git a/app/controllers/about_controller.rb b/app/controllers/about_controller.rb
index c0addbeccc6..47690e81eb9 100644
--- a/app/controllers/about_controller.rb
+++ b/app/controllers/about_controller.rb
@@ -4,7 +4,10 @@ class AboutController < ApplicationController
   before_action :set_body_classes
   before_action :set_instance_presenter, only: [:show, :more, :terms]
 
-  def show; end
+  def show
+    serializable_resource = ActiveModelSerializers::SerializableResource.new(InitialStatePresenter.new(initial_state_params), serializer: InitialStateSerializer)
+    @initial_state_json   = serializable_resource.to_json
+  end
 
   def more; end
 
@@ -15,6 +18,7 @@ class AboutController < ApplicationController
   def new_user
     User.new.tap(&:build_account)
   end
+
   helper_method :new_user
 
   def set_instance_presenter
@@ -24,4 +28,11 @@ class AboutController < ApplicationController
   def set_body_classes
     @body_classes = 'about-body'
   end
+
+  def initial_state_params
+    {
+      settings: {},
+      token: current_session&.token,
+    }
+  end
 end
diff --git a/app/controllers/admin/settings_controller.rb b/app/controllers/admin/settings_controller.rb
index f27a1f4d450..29b590d7a3d 100644
--- a/app/controllers/admin/settings_controller.rb
+++ b/app/controllers/admin/settings_controller.rb
@@ -11,8 +11,15 @@ module Admin
       site_terms
       open_registrations
       closed_registrations_message
+      open_deletion
+      timeline_preview
+    ).freeze
+
+    BOOLEAN_SETTINGS = %w(
+      open_registrations
+      open_deletion
+      timeline_preview
     ).freeze
-    BOOLEAN_SETTINGS = %w(open_registrations).freeze
 
     def edit
       @settings = Setting.all_as_records
diff --git a/app/controllers/home_controller.rb b/app/controllers/home_controller.rb
index 218da69066f..8a8b9ec76ba 100644
--- a/app/controllers/home_controller.rb
+++ b/app/controllers/home_controller.rb
@@ -15,12 +15,16 @@ class HomeController < ApplicationController
   end
 
   def set_initial_state_json
-    state = InitialStatePresenter.new(settings: Web::Setting.find_by(user: current_user)&.data || {},
-                                      current_account: current_account,
-                                      token: current_session.token,
-                                      admin: Account.find_local(Setting.site_contact_username))
-
-    serializable_resource = ActiveModelSerializers::SerializableResource.new(state, serializer: InitialStateSerializer)
+    serializable_resource = ActiveModelSerializers::SerializableResource.new(InitialStatePresenter.new(initial_state_params), serializer: InitialStateSerializer)
     @initial_state_json   = serializable_resource.to_json
   end
+
+  def initial_state_params
+    {
+      settings: Web::Setting.find_by(user: current_user)&.data || {},
+      current_account: current_account,
+      token: current_session.token,
+      admin: Account.find_local(Setting.site_contact_username),
+    }
+  end
 end
diff --git a/app/javascript/fonts/montserrat/Montserrat-Medium.ttf b/app/javascript/fonts/montserrat/Montserrat-Medium.ttf
new file mode 100644
index 00000000000..88d70b89c3f
--- /dev/null
+++ b/app/javascript/fonts/montserrat/Montserrat-Medium.ttf
diff --git a/app/javascript/images/cloud2.png b/app/javascript/images/cloud2.png
new file mode 100644
index 00000000000..f325ca6de09
--- /dev/null
+++ b/app/javascript/images/cloud2.png
diff --git a/app/javascript/images/cloud3.png b/app/javascript/images/cloud3.png
new file mode 100644
index 00000000000..ab194d0b857
--- /dev/null
+++ b/app/javascript/images/cloud3.png
diff --git a/app/javascript/images/cloud4.png b/app/javascript/images/cloud4.png
new file mode 100644
index 00000000000..98323f5a271
--- /dev/null
+++ b/app/javascript/images/cloud4.png
diff --git a/app/javascript/images/elephant-fren.png b/app/javascript/images/elephant-fren.png
new file mode 100644
index 00000000000..3b64edf084c
--- /dev/null
+++ b/app/javascript/images/elephant-fren.png
diff --git a/app/javascript/images/logo.svg b/app/javascript/images/logo.svg
index c233db84281..16cb3a94407 100644
--- a/app/javascript/images/logo.svg
+++ b/app/javascript/images/logo.svg
@@ -1 +1 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1000 1000" height="1000" width="1000"><path d="M500 0a500 500 0 0 0-353.553 146.447 500 500 0 1 0 707.106 707.106A500 500 0 0 0 500 0zm-.059 280.05h107.12c-19.071 13.424-26.187 51.016-27.12 73.843V562.05c0 44.32-35.68 80-80 80s-80-35.68-80-80v-202c0-44.32 35.68-80 80-80zm-.441 52c-15.464 0-28 12.537-28 28 0 15.465 12.536 28 28 28s28-12.535 28-28c0-15.463-12.536-28-28-28zm-279.059 7.9c44.32 0 80 35.68 80 80v206.157c.933 22.827 8.049 60.42 27.12 73.842H220.44c-44.32 0-80-35.68-80-80v-200c0-44.32 35.68-80 80-80zm559.12 0c44.32 0 80 35.68 80 80v200c0 44.32-35.68 80-80 80H672.44c19.071-13.424 26.187-51.016 27.12-73.843V419.95c0-44.32 35.68-80 80-80zM220 392c-15.464 0-28 12.536-28 28s12.536 28 28 28 28-12.536 28-28-12.536-28-28-28zm560 0c-15.464 0-28 12.536-28 28s12.536 28 28 28 28-12.536 28-28-12.536-28-28-28zm-280.5 40.05c-15.464 0-28 12.537-28 28 0 15.465 12.536 28 28 28s28-12.535 28-28c0-15.463-12.536-28-28-28zM220 491.95c-15.464 0-28 12.535-28 28 0 15.463 12.536 28 28 28s28-12.537 28-28c0-15.465-12.536-28-28-28zm560 0c-15.464 0-28 12.535-28 28 0 15.463 12.536 28 28 28s28-12.537 28-28c0-15.465-12.536-28-28-28zM499.5 532c-15.464 0-28 12.536-28 28s12.536 28 28 28 28-12.536 28-28-12.536-28-28-28zM220 591.95c-15.464 0-28 12.535-28 28 0 15.463 12.536 28 28 28s28-12.537 28-28c0-15.465-12.536-28-28-28zm560 0c-15.464 0-28 12.535-28 28 0 15.463 12.536 28 28 28s28-12.537 28-28c0-15.465-12.536-28-28-28z" fill="#189efc"/></svg>
\ No newline at end of file
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1000 1000" height="1000" width="1000"><path d="M500 0a500 500 0 0 0-353.553 146.447 500 500 0 1 0 707.106 707.106A500 500 0 0 0 500 0zm-.059 280.05h107.12c-19.071 13.424-26.187 51.016-27.12 73.843V562.05c0 44.32-35.68 80-80 80s-80-35.68-80-80v-202c0-44.32 35.68-80 80-80zm-.441 52c-15.464 0-28 12.537-28 28 0 15.465 12.536 28 28 28s28-12.535 28-28c0-15.463-12.536-28-28-28zm-279.059 7.9c44.32 0 80 35.68 80 80v206.157c.933 22.827 8.049 60.42 27.12 73.842H220.44c-44.32 0-80-35.68-80-80v-200c0-44.32 35.68-80 80-80zm559.12 0c44.32 0 80 35.68 80 80v200c0 44.32-35.68 80-80 80H672.44c19.071-13.424 26.187-51.016 27.12-73.843V419.95c0-44.32 35.68-80 80-80zM220 392c-15.464 0-28 12.536-28 28s12.536 28 28 28 28-12.536 28-28-12.536-28-28-28zm560 0c-15.464 0-28 12.536-28 28s12.536 28 28 28 28-12.536 28-28-12.536-28-28-28zm-280.5 40.05c-15.464 0-28 12.537-28 28 0 15.465 12.536 28 28 28s28-12.535 28-28c0-15.463-12.536-28-28-28zM220 491.95c-15.464 0-28 12.535-28 28 0 15.463 12.536 28 28 28s28-12.537 28-28c0-15.465-12.536-28-28-28zm560 0c-15.464 0-28 12.535-28 28 0 15.463 12.536 28 28 28s28-12.537 28-28c0-15.465-12.536-28-28-28zM499.5 532c-15.464 0-28 12.536-28 28s12.536 28 28 28 28-12.536 28-28-12.536-28-28-28zM220 591.95c-15.464 0-28 12.535-28 28 0 15.463 12.536 28 28 28s28-12.537 28-28c0-15.465-12.536-28-28-28zm560 0c-15.464 0-28 12.535-28 28 0 15.463 12.536 28 28 28s28-12.537 28-28c0-15.465-12.536-28-28-28z" fill="#fff"/></svg>
diff --git a/app/javascript/mastodon/components/dropdown_menu.js b/app/javascript/mastodon/components/dropdown_menu.js
index 12e1b44fa22..98323b0691d 100644
--- a/app/javascript/mastodon/components/dropdown_menu.js
+++ b/app/javascript/mastodon/components/dropdown_menu.js
@@ -14,6 +14,7 @@ export default class DropdownMenu extends React.PureComponent {
     size: PropTypes.number.isRequired,
     direction: PropTypes.string,
     ariaLabel: PropTypes.string,
+    disabled: PropTypes.bool,
   };
 
   static defaultProps = {
@@ -68,9 +69,19 @@ export default class DropdownMenu extends React.PureComponent {
   }
 
   render () {
-    const { icon, items, size, direction, ariaLabel } = this.props;
-    const { expanded } = this.state;
+    const { icon, items, size, direction, ariaLabel, disabled } = this.props;
+    const { expanded }   = this.state;
     const directionClass = (direction === 'left') ? 'dropdown__left' : 'dropdown__right';
+    const iconStyle      = { fontSize: `${size}px`, width: `${size}px`, lineHeight: `${size}px` };
+    const iconClassname  = `fa fa-fw fa-${icon} dropdown__icon`;
+
+    if (disabled) {
+      return (
+        <div className='icon-button disabled' style={iconStyle} aria-label={ariaLabel}>
+          <i className={iconClassname} aria-hidden />
+        </div>
+      );
+    }
 
     const dropdownItems = expanded && (
       <ul className='dropdown__content-list'>
@@ -80,8 +91,8 @@ export default class DropdownMenu extends React.PureComponent {
 
     return (