docs(wechat): Default scope

* WeChat default SCOPE changed from snsapi_login to snsapi_userinfo

* add description in doc, weixin default scope is snsapi_login, bug user can config it

docs/providers.rst

@@ -1391,13 +1391,15 @@ will support open platform by default, which value is
 ``https://open.weixin.qq.com/connect/qrconnect``.
 
 You can optionally specify additional scope to use. If no ``SCOPE`` value
-is set, will use ``snsapi_login`` by default.
+is set, will use ``snsapi_login`` by default(for Open Platform Account, need
+registration). Other ``SCOPE`` options are: snsapi_base, snsapi_userinfo.
 
 .. code-block:: python
 
     SOCIALACCOUNT_PROVIDERS = {
         'weixin': {
             'AUTHORIZE_URL': 'https://open.weixin.qq.com/connect/oauth2/authorize',  # for media platform
+            'SCOPE': ['snsapi_base'],
         }
     }