Add Sites worker entrypoint

worker/index.js

@@ -0,0 +1,18 @@
+const worker = {
+    async fetch(request, env) {
+        const response = await env.ASSETS.fetch(request);
+
+        if (
+            response.status !== 404 ||
+            request.method !== 'GET' ||
+            !request.headers.get('accept')?.includes('text/html')
+        ) {
+            return response;
+        }
+
+        const indexUrl = new URL('/index.html', request.url);
+        return env.ASSETS.fetch(new Request(indexUrl, request));
+    },
+};
+
+export default worker;