feat(fennel): add fennel module (#4717)

docs/config/README.md

@@ -283,6 +283,7 @@ $dotnet\
 $elixir\
 $elm\
 $erlang\
+$fennel\
 $golang\
 $guix_shell\
 $haskell\
@@ -1475,6 +1476,45 @@ By default the module will be shown if any of the following conditions are met:
 format = 'via [e $version](bold red) '
 ```
 
+## Fennel
+
+The `fennel` module shows the currently installed version of [Fennel](https://fennel-lang.org).
+By default the module will be shown if any of the following conditions are met:
+
+- The current directory contains a file with the `.fnl` extension
+
+### Options
+
+| Option              | Default                              | Description                                                               |
+| ------------------- | ------------------------------------ | ------------------------------------------------------------------------- |
+| `format`            | `'via [$symbol($version )]($style)'` | The format for the module.                                                |
+| `version_format`    | `'v${raw}'`                          | The version format. Available vars are `raw`, `major`, `minor`, & `patch` |
+| `symbol`            | `'🧅 '`                              | The symbol used before displaying the version of fennel.                  |
+| `style`             | `'bold green'`                       | The style for the module.                                                 |
+| `detect_extensions` | `[fnl]`                              | Which extensions should trigger this module.                              |
+| `detect_files`      | `[]`                                 | Which filenames should trigger this module.                               |
+| `detect_folders`    | `[]`                                 | Which folders should trigger this modules.                                |
+| `disabled`          | `false`                              | Disables the `fennel` module.                                             |
+
+### Variables
+
+| Variable | Example  | Description                          |
+| -------- | -------- | ------------------------------------ |
+| version  | `v1.2.1` | The version of `fennel`              |
+| symbol   |          | Mirrors the value of option `symbol` |
+| style\*  |          | Mirrors the value of option `style`  |
+
+*: This variable can only be used as a part of a style string
+
+### Example
+
+```toml
+# ~/.config/starship.toml
+
+[fennel]
+symbol = '⫰ '
+```
+
 ## Fill
 
 The `fill` module fills any extra space on the line with a symbol. If multiple `fill` modules are