add url for raw files w/ commit hash

frontend.js

@@ -1,4 +1,17 @@
 export class Frontend {
+  repoUrl(user, repo) {
+    
+  }
+
+  rawUrl(user, repo, commit, path) {
+    return (
+      this.appBaseUrl +
+      '/raw/commit' +
+      '/' + encodeURIComponent(commit) +
+      '/' + encodeURI(path)
+    )
+  }
+
   async serve(event) {
     // TODO: load files from different mounted repos
     event.respondWith(new Response(