Add slash command capabilities

[AardWolf]

Minluck seems like a good place to start and enhance the capabilities. First slash commands, then response menus (if multiple mice were found), then typeahead capabilities for mice.

instead of "multiple matches" it can now use the menu: https://discordjs.guide/interactions/select-menus.html#building-and-sending-select-menus
and I think we can add autotype for mice: https://discordjs.guide/interactions/autocomplete.html

[AardWolf]

#255 moved this to prod.

Still need to add permissions checks to the interaction processor

[bradp]

Tagging myself in this as I've started work on adding additional slash commands 🎉