chore: update middleware changeset (#6986)

.changeset/pretty-bears-deliver.md

@@ -2,4 +2,46 @@
 'astro': minor
 ---
 
-New middleware API
+Implements a new experimental middleware in Astro.
+
+The middleware is available under the following experimental flag:
+
+```js
+export default defineConfig({
+    experimental: {
+        middleware: true
+    }
+})
+```
+
+Or via CLI, using the new argument `--experimental-middleware`.
+
+Create a file called `middleware.{js,ts}` inside the `src` folder, and 
+export a `onRequest` function. 
+
+From `astro/middleware`, use the `defineMiddleware` utility to take advantage of type-safety, and use
+the `sequence` utility to chain multiple middleware functions.
+
+Example:
+
+```ts
+import {defineMiddleware, sequence} from "astro/middleware";
+
+const redirects = defineMiddleware((context, next) => {
+  if (context.request.url.endsWith("/old-url")) {
+    return context.redirect("/new-url")    
+  }
+  return next();
+});
+
+const minify = defineMiddleware(async (context, next) => {
+  const repsonse = await next();
+  const minifiedHtml = await minifyHtml(response.text());
+  return new Response(minifiedHtml, {
+    status: 200,
+    headers: response.headers
+  });
+})
+
+export const onRequest = sequence(redirects, minify);
+```