[chore] Release 4.8.0

- Bumped version to 4.8.0
- Includes #412 #485 #492

Author: lahirumaramba

firebase.go

@@ -38,7 +38,7 @@ import (
 var defaultAuthOverrides = make(map[string]interface{})
 
 // Version of the Firebase Go Admin SDK.
-const Version = "4.7.1"
+const Version = "4.8.0"
 
 // firebaseEnvName is the name of the environment variable with the Config.
 const firebaseEnvName = "FIREBASE_CONFIG"