refs https://github.com/TryGhost/Toolbox/issues/81
- the existing `label-actions` tooling was deprecated and shut down but
after reviewing, it wasn't expressive enough for our workflow use cases
- we wanted a tool we could drop into our repos and it works without
extra configuration
- I've developed the `tryghost/label-actions` GitHub Action which will
supports all our labeling flows for triaging
- this commit switches the repo over to using that
- configured the scheduled tasks to run at midnight daily
