feat(/manage-tag): add option for registering a tag as a guild command

[kyranet]

Up to 100 guild commands, and the tag name would be sanitised to comply with Discord's format requirements.

A new option in /manage-tag create and /manage-tag edit would be made to support (de)registering a tag as a slash command, which would be handled using the unknown chat input command event. This new option could be named one of publish, create-slash, use-slash, or a better option where there be any.