docs: add plugin file scoping (includes) documentation

src/content/docs/linter/plugins.mdx

@@ -30,22 +30,33 @@ the following configuration:
 ```
 
 The plugin will now be enabled on all supported files the linter runs on. You
-can see its results when running `biome lint` or `biome check`. For example:
+can see its results when running `biome lint` or `biome check`.
 
-```shell
-$ biome lint
-/packages/tailwindcss-config-analyzer/src/introspect.ts:12:17 plugin ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+## File Scoping
 
-  ✖ Prefer object spread instead of `Object.assign()`
+By default, a plugin runs on every file the linter processes. If a plugin only
+applies to certain files, you can restrict it using `includes` glob patterns.
+Use negated globs (prefixed with `!`) for exclusions:
 
-    10 │ function createContextFromConfig(config: Partial<Config>) {
-    11 │        return createContext(
-  > 12 │                resolveConfig(Object.assign({}, DEFAULT_CONFIG, config)),
-       │                              ^^^^^^^^^^^^^
-    13 │        );
-    14 │ }
+```json name="biome.json"
+{
+    "plugins": [
+        {
+            "path": "./react-plugin.grit",
+            "includes": ["src/components/**"]
+        },
+        {
+            "path": "./ts-only-plugin.grit",
+            "includes": ["src/**/*.ts", "!**/*.test.ts"]
+        }
+    ]
+}
 ```
 
+When `includes` is set, the plugin only runs on files matching at least one of
+the patterns. Negated patterns act as exceptions. Patterns follow the
+[glob syntax reference](/reference/configuration/#glob-syntax-reference).
+
 ## Target Languages
 
 A GritQL snippet always attempts to match against a given _target language_.

src/content/docs/reference/configuration.mdx

@@ -50,6 +50,46 @@ This is required so Biome can orchestrate multiple files in CLI and editors at t
 
 > Default: `true`
 
+## `plugins`
+
+A list of [GritQL plugins](/linter/plugins/) to enable. Each entry can be
+either a simple path string or an object with a path and optional file-scoping
+options.
+
+Simple path:
+
+```json title="biome.json"
+{
+  "plugins": ["./my-plugin.grit"]
+}
+```
+
+Path with file scoping:
+
+```json title="biome.json"
+{
+  "plugins": [
+    {
+      "path": "./react-plugin.grit",
+      "includes": ["src/components/**", "!src/components/generated/**"]
+    }
+  ]
+}
+```
+
+You can mix both forms in the same list.
+
+### `plugins.<ITEM>.path`
+
+Path to the plugin file (`.grit`) or plugin directory containing a
+`biome-manifest.jsonc`.
+
+### `plugins.<ITEM>.includes`
+
+A list of [glob patterns](#glob-syntax-reference) for files the plugin should
+run on. Use negated globs (prefixed with `!`) for exclusions.
+
+When omitted, the plugin runs on every file the linter processes.
 
 ## `files`