Persistent rooms via Firebase (#2188)

* Periodically back up collaborative rooms in firebase

* Responses to code review

* comments from code review, new firebase credentials

src/global.d.ts

@@ -20,6 +20,7 @@ declare namespace NodeJS {
     readonly REACT_APP_BACKEND_V2_GET_URL: string;
     readonly REACT_APP_BACKEND_V2_POST_URL: string;
     readonly REACT_APP_SOCKET_SERVER_URL: string;
+    readonly REACT_APP_FIREBASE_CONFIG: string;
   }
 }