Swipe right in room to get back to overview

So I really like that I can swipe my most recent chats into view or my communities, but I don't think this is being communicated at all and I am always surprised it's there when I do it by accident.
I like how discord does it a lot more, where you swipe the whole chat window to the left/right instead of swiping the bar in, which currently kind of appears out of nowhere.

this obviously needs to consider: https://github.com/vector-im/riotX-android/issues/422#issuecomment-543891517

Telegram also does a similar thing + swipe to reply. not sure if i like seeing users quickly or swipe to reply more though personally.

Also if swiping the chat moves the chat window and reveals what's beneath it, it would probably just be the chats and not recently used chats :/

What I really like about both telegram and discord is that I can swipe the left menu without getting really close to the border, since that doesn't only feel more abitrary to me, it also often conflicts with Android 10 gestures.

Start with the issue description and the linked discussion in riotX-android#422 to understand the competing swipe behaviors and constraints. Before implementation, settle the intended interaction for returning to the overview, recently used chats, and swipe-to-reply; done means the agreed behavior works without conflicting with Android 10 gestures.

Written by the indexing model from the issue text.