Add Riot client

[encadyma]

Replace matrix.ocf.berkeley.edu with Riot client maybe

[cg505]

If we want to do this, it should be on another domain: see element-hq/element-web#1977. That said, just using riot.im/app seems perfectly fine.

[nikhiljha]

I think the main thing is if we host our own Riot then it can prefill the homeserver address correctly. If we tell people to use riot.im/app then they'll need to fill it in manually.

So maybe riot.ocf.berkeley.edu?

[encadyma]

Seems like a good idea, though as a note I believe riot is already the name of a staff VM, so we would have to choose something else

[emmatyping]

Perhaps https://chat.ocf.berkeley.edu ?