Shutdown command

[MoonlightCapital]

Please check the following boxes

• [x] I've read and agree to the Contribution Guidelines and to the Code of Conduct
  • [x] I've checked that I didn't commit sensitive information like tokens or other login information
  • [x] I haven't hardcoded any IDs or anything else that shouldn't be (with the exception being permissions)
  • [x] I tested my code and I verified it's working to the best of my ability
  • [x] I checked if my code doesn't violate the styleguide with npm test

Describe your pull request

Adds a command that allows moderators to shut down the bot in case it crashes