Add ?roshan Command

[mdiller]

A new command that give some basic info about roshan, like respawn times, item drops, and how his hp/armor increases. The downside of this kind of command is that dota is an ever-changing game, and I'd have to make sure to maintain it, which would have to be done manually, as I can't can extract this kind of info from the game files.

https://discord.com/channels/296486417197170688/296488428726648833/905714855443578910