Add database emulator and rules

Author: michaelprichardson

test/database.rules.json

@@ -0,0 +1,6 @@
+{
+  "rules": {
+    ".read": true,
+    ".write": true
+  }
+}

test/firebase.json

@@ -2,12 +2,18 @@
   "firestore": {
     "rules": "firestore.rules"
   },
+  "database": {
+    "rules": "database.rules.json"
+  },
   "emulators": {
     "auth": {
       "port": 9099
     },
     "firestore": {
       "port": 8080
+    },
+    "database": {
+      "port": 9000
     }
   }
 }