Refresh token documentation

[ShriramK]

Please update the documentation on refresh token at https://docs.authlib.org/en/latest/client/frameworks.html or https://docs.authlib.org/en/latest/client/flask.html as per the suggested solution at https://stackoverflow.com/questions/62293888/obtaining-and-storing-refresh-token-using-authlib-with-flask

Parameter to specify add in the remote application as per " .. The first step is register a remote application on the OAuth registry via oauth.register method " at https://docs.authlib.org/en/latest/client/flask.html to obtain retrieve get the refresh token

is

authorize_params={'access_type': 'offline'}

google = oauth.register(
    'google',
    # ...
    authorize_params={'access_type': 'offline'},
)

as per https://stackoverflow.com/a/62296675

and

'prompt': 'consent' in the client_kwargs parameter in the remote application on the OAuth registry via oauth.register method

if required

client_kwargs = {'prompt':'consent'} as per https://stackoverflow.com/questions/62293888/obtaining-and-storing-refresh-token-using-authlib-with-flask#comment110182471_62296675

Thank you