feat: Add Crystal version module (#170)

docs/config/README.md

@@ -116,6 +116,7 @@ prompt_order = [
     "memory_usage",
     "aws",
     "env_var",
+    "crystal",
     "cmd_duration",
     "line_break",
     "jobs",
@@ -858,6 +859,33 @@ separator = "/"
 style = "bold dimmed green"
 ```
 
+## Crystal
+
+The `crystal` module shows the currently installed version of Crystal.
+The module will be shown if any of the following conditions are met:
+
+- The current directory contains a `shard.yml` file
+- The current directory contains a `.cr` file
+
+### Options
+
+| Variable   | Default      | Description                                                  |
+| ---------- | ------------ | ------------------------------------------------------------ |
+| `symbol`   | `"🔮 "`      | The symbol used before displaying the version of crystal.    |
+| `style`    | `"bold red"` | The style for the module.                                    |
+| `disabled` | `false`      | Disables the `crystal` module.                               |
+
+### Example
+
+```toml
+# ~/.config/starship.toml
+
+[crystal]
+symbol = "🔮 "
+style = "bold red"
+disabled = false
+```
+
 ## NodeJS
 
 The `nodejs` module shows the currently installed version of NodeJS.