Use a la carte Firebase packages

Instead of pulling in the master Firebase package as a dependency, use a
la carte Firebase packages for the Firebase components that we actually
use—namely `@firebase/app` (the core), `@firebase/auth`, and
`@firebase/database`. Also add `@firebase/app-types` as a dependency to
satisfy the peer dependency of the aforementioned packages.

Just requires changing the imports in the `appFirebase` service to
target the individual packages, and everything seems to work just fine.

Author: Mat Brown

package.json

@@ -146,6 +146,10 @@
   "bugs": "https://trello.com/b/ONaFg6wh/popcode",
   "license": "MIT",
   "dependencies": {
+    "@firebase/app": "^0.1.10",
+    "@firebase/app-types": "^0.1.0",
+    "@firebase/auth": "^0.3.4",
+    "@firebase/database": "^0.1.11",
     "PrettyCSS": "^0.3.17",
     "array-to-sentence": "^2.0.0",
     "bowser": "^1.4.5",
@@ -157,7 +161,6 @@
     "enumify": "^1.0.4",
     "es6-set": "^0.1.4",
     "esprima": "^3.0.0",
-    "firebase": "^4.1.3",
     "github-api": "^3.0.0",
     "hast-util-sanitize": "^1.1.1",
     "highlight.js": "^9.12.0",

src/services/appFirebase.js

@@ -1,6 +1,6 @@
-import firebase from 'firebase/app';
-import 'firebase/auth';
-import 'firebase/database';
+import {firebase} from '@firebase/app';
+import '@firebase/auth';
+import '@firebase/database';
 import config from '../config';
 
 const appFirebase = firebase.initializeApp({