OAuth2Session Google API example note documentation

[ShriramK]

Please add or note in the documentation examples
how passing request body as json than data parameter ( .post(json=) instead of .post(data=) )
for a HTTP post call via OAuth2Session ( Session ' s request ) 's required for Google APIs .

Reference -
Calendar API example at
https://stackoverflow.com/questions/29714710/google-calendar-api-freebusy-jquery-post-gets-400-bad-request-error