Add whitelisting (combined with making green)

[Danyc0]

Modify the green command to be something like:
\join
which whitelists that username and gives it the appropriate colours based on their discord roles

Could also combine this with giving access to #minecraft, in which case the command should be something like \minecraft or \mc, however then only those who have the game can join the chat, whilst others might be interested in discussing it even if they don't have the game