Support RIST

[tmatth]

Describe the feature

RIST is designed to reliably transport video over the Internet for any use case, but is typically used for professional media workflows such as news and sports contribution, remote production, affiliate distribution and primary distribution.
Source: https://www.rist.tv/

It's mainly intended for low-latency transmission over unreliable connections (e.g., commercial internet), so has a similar audience as SRT but probably made different tradeoffs as it was designed collaboratively by multiple companies as opposed to a single vendor (see: https://code.videolan.org/rist/librist#why-do-you-not-improve-srt-rather-than-starting-a-new-project)

Lastly, OBS now supports RIST muxing as of:
obsproject/obs-studio@258365d

and so this transport will soon be available to a much wider range of users client-side, but there is a lack of free software servers supporting RIST ingest.