[Feature] Add ability to inhibit notifications through DBus

[ErikReider]

Fixes: #147

Allows any application to inhibit notifications from popping up

Todo:

• [x] Logic for inhibiting
• [x] Inhibitors widget displaying how many and with a button to clear inhibitors
  • [x] Widget
  • [x] CSS
  • [x] Config schema
  • [x] Man pages
• [x] Update client with new commands
  • [x] Client update
  • [x] Update --help page
  • [x] Man page
  • [x] Client command completions
• [x] README
  • [x] Update Waybar example