Using a label applied to a PR, trigger the correct changie batch command

[Matthew Hodgkins]

eg. if a label @emitter/minor is added:

• check that a change has been made to the relevant files (apps/emitter)
• run changie batch minor
• run changie merge
• Commit the change, then use the CHANGELOG change as the release trigger like here: https://changie.dev/integrations/release-trigger/