feat: add support for xonsh (#2807)

* feat: add support for xonsh

* xonsh: add STARSHIP_SESSION_KEY

* xonsh: implement STARSHIP_SESSION_KEY in xonsh

* docs: mention tcsh, elvish, and nu in more places

* xonsh: change STARSHIP_SESSION_KEY implementation

See https://github.com/starship/starship/pull/2807#discussion_r667064149

* xonsh: fix jobs implementation

* xonsh: do not silently discard stderr from starship

3 files changed, 16 insertions, 4 deletions

diff --git a/docs/.vuepress/config.js b/docs/.vuepress/config.js
index 92249c3b6..679e4bb93 100644
--- a/docs/.vuepress/config.js
+++ b/docs/.vuepress/config.js
@@ -50,13 +50,13 @@ module.exports = {
   head: [
     ["link", { rel: "icon", href: "/icon.png" }],
     ["meta", { property: "og:title", content: "Starship: Cross-Shell Prompt" }],
-    ["meta", { property: "og:description", content: "Starship is the minimal, blazing fast, and extremely customizable prompt for any shell! Shows the information you need, while staying sleek and minimal. Quick installation available for Bash, Fish, ZSH, Ion, and Powershell."}],
+    ["meta", { property: "og:description", content: "Starship is the minimal, blazing fast, and extremely customizable prompt for any shell! Shows the information you need, while staying sleek and minimal. Quick installation available for Bash, Fish, ZSH, Ion, Tcsh, Elvish, Nu, Xonsh, and Powershell."}],
     ["meta", { property: "og:type", content: "website" }],
     ["meta", { property: "og:url", content: "https://starship.rs/" }],
     ["meta", { property: "og:image", content: "https://starship.rs/icon.png" }],
     ["meta", { name: "twitter:card", content: "summary"}],
     ["meta", { name: "twitter:title", content: "Starship: Cross-Shell Prompt"}],
-    ["meta", { name: "twitter:description", content: "Starship is the minimal, blazing fast, and extremely customizable prompt for any shell! Shows the information you need, while staying sleek and minimal. Quick installation available for Bash, Fish, ZSH, Ion, and Powershell."}],
+    ["meta", { name: "twitter:description", content: "Starship is the minimal, blazing fast, and extremely customizable prompt for any shell! Shows the information you need, while staying sleek and minimal. Quick installation available for Bash, Fish, ZSH, Ion, Tcsh, Elvish, Nu, Xonsh, and Powershell."}],
     ["meta", { name: "twitter:image", content: "https://starship.rs/icon.png"}],
     ["meta", { name: "twitter:alt", content: "Starship: Cross-Shell Prompt"}],
   ],
diff --git a/docs/README.md b/docs/README.md
index 9ba9a4ae8..4014bfc2b 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -16,7 +16,7 @@ footer: ISC Licensed | Copyright © 2019-present Starship Contributors
 
 # Used for the description meta tag, for SEO
 metaTitle: "Starship: Cross-Shell Prompt"
-description: Starship is the minimal, blazing fast, and extremely customizable prompt for any shell! Shows the information you need, while staying sleek and minimal. Quick installation available for Bash, Fish, ZSH, Ion, and PowerShell.
+description: Starship is the minimal, blazing fast, and extremely customizable prompt for any shell! Shows the information you need, while staying sleek and minimal. Quick installation available for Bash, Fish, ZSH, Ion, Tcsh, Elvish, Nu, Xonsh, and PowerShell.
 ---
 
 <div class="center">
@@ -106,6 +106,7 @@ description: Starship is the minimal, blazing fast, and extremely customizable p
 
    eval $(starship init ion)
    ```
+
    #### Elvish
 
    ::: warning
@@ -130,7 +131,7 @@ description: Starship is the minimal, blazing fast, and extremely customizable p
    eval `starship init tcsh`
    ```
 
-    #### Nushell
+   #### Nushell
 
    ::: warning
    This will change in the future.
@@ -147,3 +148,13 @@ description: Starship is the minimal, blazing fast, and extremely customizable p
    ]
    prompt = "starship_prompt"
    ```
+
+   #### Xonsh
+
+   Add the following to the end of `~/.xonshrc`:
+
+   ```sh
+   # ~/.xonshrc
+
+   execx($(starship init xonsh))
+   ```
diff --git a/docs/config/README.md b/docs/config/README.md
index 635eff5ff..01c305fe1 100644
--- a/docs/config/README.md
+++ b/docs/config/README.md
@@ -2587,6 +2587,7 @@ To enable it, set `disabled` to `false` in your configuration file.
 | `ion_indicator`        | `ion`         | A format string used to represent ion.                       |
 | `elvish_indicator`     | `esh`         | A format string used to represent elvish.                    |
 | `tcsh_indicator`       | `tsh`         | A format string used to represent tcsh.                      |
+| `xonsh_indicator`      | `xsh`         | A format string used to represent xonsh.                     |
 | `unknown_indicator`    |               | The default value to be displayed when the shell is unknown. |
 | `format`               | `$indicator ` | The format for the module.                                   |
 | `disabled`             | `true`        | Disables the `shell` module.                                 |