update default login scopes for github

backend/oauth_login.json

@@ -3,7 +3,7 @@
     "auth_url": "https://github.com/login/oauth/authorize",
     "token_url": "https://github.com/login/oauth/access_token",
     "userinfo_url": "https://api.github.com/user",
-    "scopes": ["read:user"]
+    "scopes": ["read:user", "user:email"]
   },
   "gitlab": {
     "auth_url": "https://gitlab.com/oauth/authorize",