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