Add "Add Bot" button on bot profiles + in-app invite link popup support

Not only that, but the screen we currently have when choosing where to add the bot to, is buggy and partially unusable on mobile, because if I select another community other than what's already selected by default, the screen turns black and I can't do anything further. So that screen needs to be fixed for mobile users using Firefox-like(or Mozilla-based) browsers(which is what I use).