docs(compress): add contentTypeFilter option

docs/middleware/builtin/compress.md

@@ -30,3 +30,32 @@ The compression scheme to allow for response compression. Either `gzip` or `defl
 ### <Badge type="info" text="optional" /> threshold: `number`
 
 The minimum size in bytes to compress. Defaults to 1024 bytes.
+
+### <Badge type="info" text="optional" /> contentTypeFilter: `RegExp` | `(contentType: string) => boolean`
+
+A `RegExp` or function to determine whether the response should be compressed based on its `Content-Type`. By default, a built-in list of compressible Content-Types is used.
+
+You can pass a `RegExp` to compress only matching Content-Types:
+
+```ts
+// Compress only JSON responses
+app.use(compress({ contentTypeFilter: /^application\/json/ }))
+```
+
+Or pass a function for custom logic. The built-in `COMPRESSIBLE_CONTENT_TYPE_REGEX` is also exported so you can extend the default behavior:
+
+```ts
+import {
+  compress,
+  COMPRESSIBLE_CONTENT_TYPE_REGEX,
+} from 'hono/compress'
+
+// Compress the default Content-Types plus a custom one
+app.use(
+  compress({
+    contentTypeFilter: (type) =>
+      COMPRESSIBLE_CONTENT_TYPE_REGEX.test(type) ||
+      type === 'application/x-myformat',
+  })
+)
+```