Add default fetch method to worker

contact-email-worker/src/index.ts

@@ -2,6 +2,10 @@ import { EmailMessage } from "cloudflare:email";
 import { WorkerEntrypoint } from "cloudflare:workers";
 
 export default class SendEmailWorker extends WorkerEntrypoint<Env> {
+  async fetch() {
+    return new Response("Unimplemented");
+  }
+
   async sendEmail(rawMessage: string): Promise<Response> {
     try {
       const cfMessage = new EmailMessage(