RoyalGuard v2.3

Release v2.3:

• Updated serenity and all dependencies to their latest compatible versions
  (Note: tokio 0.3 doesn't work with serenity due to higher-up dependencies also not being compatible)
• Changed the welcome roles subcommand to autoroles. This makes it more intuitive for users to actually work
  with this command.

Please let me know in regards to any bugs in the issues tab!