Two dev documents says different things about supported image formats:
https://dev.twitter.com/rest/public/uploading-media
https://dev.twitter.com/rest/reference/post/media/upload
The former says Twitter does not supports BMP and the latter says Twitter does.
https://twittercommunity.com/t/why-this-image-couldnt-be-uploaded-to-twitter/8975?source_topic_id=58596
Someone answered that Twitter in fact does not, and if so please correct the document.
