Version 4.20 mdzn release

So named because @miedzinski contributed all of this release's material and requested it. I guess I'm a sucker for polite requests. Plus it's better than an overused weed reference right?

• Implementation of GetFriendList as user.friend and user.friend_list
• Ensure proper typing in certain steam.user class members
• Add user.bans.game_count, exposing NumberOfGameBans