Add Markdown diagrams and render hooks for code blocks

You can now create custom hook templates for code blocks, either one for all (`render-codeblock.html`) or for a given code language (e.g. `render-codeblock-go.html`).

We also used this new hook to add support for diagrams in Hugo:

* Goat (Go ASCII Tool) is built-in and enabled by default; just create a fenced code block with the language `goat` and start draw your Ascii diagrams.
* Another popular alternative for diagrams in Markdown, Mermaid (supported by GitHub), can also be implemented with a simple template. See the Hugo documentation for more information.

Updates #7765
Closes #9538
Fixes #9553
Fixes #8520
Fixes #6702
Fixes #9558

1 files changed, 3 insertions, 7 deletions

diff --git a/hugolib/site_sections.go b/hugolib/site_sections.go
index ae343716e..50dfe6ffa 100644
--- a/hugolib/site_sections.go
+++ b/hugolib/site_sections.go
@@ -19,14 +19,10 @@ import (
 
 // Sections returns the top level sections.
 func (s *SiteInfo) Sections() page.Pages {
-	home, err := s.Home()
-	if err == nil {
-		return home.Sections()
-	}
-	return nil
+	return s.Home().Sections()
 }
 
 // Home is a shortcut to the home page, equivalent to .Site.GetPage "home".
-func (s *SiteInfo) Home() (page.Page, error) {
-	return s.s.home, nil
+func (s *SiteInfo) Home() page.Page {
+	return s.s.home
 }