Forward cdn-cgi/scripts paths to Cloudflare (#422)

* Forward cdn-cgi/scripts paths to Cloudflare

Right now, Miniflare 404s on attempts to download `rocket-loader.min.js`. For folks who've set up a Worker in front of Cloudflare Pages (e.g. to handle API requests on the same domain), this breaks their web app during local development: it renders as a white screen.

This PR adds a small amount of logic to simply forward those requests onto Cloudflare.

* Update packages/http-server/src/index.ts

Co-authored-by: MrBBot <me@mrbbot.dev>

* Update index.ts

* add missing paren

Co-authored-by: MrBBot <me@mrbbot.dev>

* remove unneeded import

Co-authored-by: MrBBot <me@mrbbot.dev>

* Update index.ts

Co-authored-by: MrBBot <me@mrbbot.dev>

packages/http-server/src/index.ts

@@ -16,6 +16,7 @@ import {
   Response,
   _getBodyLength,
   _headersFromIncomingRequest,
+  fetch,
   logResponse,
 } from "@miniflare/core";
 import { Log, prefixError, randomHex } from "@miniflare/shared";
@@ -288,11 +289,19 @@ export function createRequestListener<Plugins extends HTTPPluginSignatures>(
           url
         );
         status = 200;
+        res?.writeHead(status, { "Content-Type": "text/plain; charset=UTF-8" });
+        res?.end();
+      } else if (pathname.startsWith("/cdn-cgi/scripts/")) {
+        response = await fetch(new URL(pathname, "https://cloudflare.com"));
+        status = response.status;
+        if (res) {
+          await writeResponse(response, res, HTTPPlugin.liveReload, mf.log);
+        }
       } else {
         status = 404;
+        res?.writeHead(status, { "Content-Type": "text/plain; charset=UTF-8" });
+        res?.end();
       }
-      res?.writeHead(status, { "Content-Type": "text/plain; charset=UTF-8" });
-      res?.end();
     } else {
       try {
         response = await mf.dispatchFetch(request);