add frontend class for serving frontend files from repos

frontend.js

@@ -0,0 +1,8 @@
+export class Frontend {
+  async serve(event) {
+    // TODO: load files from different mounted repos
+    event.respondWith(new Response(
+      'Not Found', {status: 404}
+    ))
+  }
+}

server.js

@@ -1,8 +1,10 @@
-import { Auth } from './auth'
+import { Auth } from "./auth"
+import { Frontend } from "./frontend"
 
 export class Server {
   constructor() {
     this.auth = new Auth()
+    this.frontend = new Frontend()
   }
 
   async getEnv(variables) {
@@ -35,9 +37,7 @@ export class Server {
     if (pathname === `${this.baseUrl}/api/auth`) {
       await this.auth.redirect(event)
     } else {
-      event.respondWith(new Response(
-        'Not Found', {status: 404}
-      ))
+      await this.frontend.serve(event)
     }
   }