added firebase and rudimentary leaderboard support

addons/godot-firebase/.env

@@ -0,0 +1,24 @@
+[firebase/environment_variables]
+
+"apiKey"="AIzaSyB9_oTvQOZp1XaqErfmrl2A0K1bm9G2_S4",
+"authDomain"="godotfps.firebaseapp.com",
+"databaseURL"="",
+"projectId"="godotfps",
+"storageBucket"="godotfps.firebasestorage.app",
+"messagingSenderId"="703030364789",
+"appId"="1:703030364789:web:dab5431813950942a2c63c",
+"measurementId"="G-XD7BKEVQL5"
+"clientId"=""
+"clientSecret"=""
+"domainUriPrefix"=""
+"functionsGeoZone"=""
+"cacheLocation"=""
+
+[firebase/emulators/ports]
+
+authentication=""
+firestore=""
+realtimeDatabase=""
+functions=""
+storage=""
+dynamicLinks=""