* Add MediaConvertWebPToPNG option (telegram).
When enabled matterbridge will convert .webp files to .png files
before uploading them to the mediaserver of the other bridges.
Fixes#398
* Add support for editing/deleting messages
* Add support for uploading files
* Add support for avatars
* Use the Rocket.Chat.Go.SDK
* Use the rest and streaming api
This uses our own gomatrix lib with the SendHTML function which
adds HTML to formatted_body in matrix.
golang-commonmark is used to convert markdown into valid HTML.