Add convo

[sjehuda]

https://git.disroot.org/badrihippo/convo @badrihippo

[badrihippo]

Oh, wow, thanks! This app isn't quite usable yet though so maybe hold off for a bit? I'll add a PR once it's ready.

(Actually I'm working on the OMEMO part right now, so who knows this might be an app that's 100% implemented OMEMO before it's 100% ready to use 😉 thanks to it being flicked from ConverseJS of course)