refactor: Informational commands

[sustained]

A quick cleanup of all our informational commands.

• [x] Rename miscellaneous command group to informational
• [x] Ensure all command names are as expected (copy-pasting woes)
• [x] Add missing examples to !coc, !code, !dry, !etiquette
• [x] Update !roles examples to match new example format
• [x] Make all informational commands DMable
  • [x] Use !sharing as the template, that's how I want them all to work
  • [x] Don't forget to set guildOnly because DMs don't have members
• [ ] Extract the most common parts of embed building to the already existing embedMessage function
  • [ ] So that means, the Vue logo, the default embed colour, the "requested by" etc.
  • [ ] Refactor all the commands to use the updated utility, where appropriate.

EDIT: See #51 for the crossed-out points.