Persistent rooms via Firebase (excalidraw#2188)

* Periodically back up collaborative rooms in firebase

* Responses to code review

* comments from code review, new firebase credentials

.env

@@ -2,3 +2,4 @@ REACT_APP_BACKEND_V1_GET_URL=https://json.excalidraw.com/api/v1/
 REACT_APP_BACKEND_V2_GET_URL=https://json.excalidraw.com/api/v2/
 REACT_APP_BACKEND_V2_POST_URL=https://json.excalidraw.com/api/v2/post/
 REACT_APP_SOCKET_SERVER_URL=https://excalidraw-socket.herokuapp.com
+REACT_APP_FIREBASE_CONFIG='{"apiKey":"AIzaSyAd15pYlMci_xIp9ko6wkEsDzAAA0Dn0RU","authDomain":"excalidraw-room-persistence.firebaseapp.com","databaseURL":"https://excalidraw-room-persistence.firebaseio.com","projectId":"excalidraw-room-persistence","storageBucket":"excalidraw-room-persistence.appspot.com","messagingSenderId":"654800341332","appId":"1:654800341332:web:4a692de832b55bd57ce0c1"}'

firebase-project/.firebaserc

@@ -0,0 +1,5 @@
+{
+  "projects": {
+    "default": "excalidraw-room-persistence"
+  }
+}

firebase-project/.gitignore

@@ -0,0 +1,66 @@
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+firebase-debug.log*
+firebase-debug.*.log*
+
+# Firebase cache
+.firebase/
+
+# Firebase config
+
+# Uncomment this if you'd like others to create their own Firebase project.
+# For a team working on the same Firebase project(s), it is recommended to leave
+# it commented so all members can deploy to the same project(s) in .firebaserc.
+# .firebaserc
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (http://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variables file
+.env

firebase-project/firebase.json

@@ -0,0 +1,6 @@
+{
+  "firestore": {
+    "rules": "firestore.rules",
+    "indexes": "firestore.indexes.json"
+  }
+}

firebase-project/firestore.indexes.json

@@ -0,0 +1,4 @@
+{
+  "indexes": [],
+  "fieldOverrides": []
+}

firebase-project/firestore.rules

@@ -0,0 +1,10 @@
+rules_version = '2';
+service cloud.firestore {
+  match /databases/{database}/documents {
+    match /{document=**} {
+      allow get, write: if true;
+      // never set this to true, otherwise anyone can delete anyone else's drawing.
+      allow list: if false;
+    }
+  }
+}