[Request] Regular docker image releases

[cgetzen]

Dockerhub has latest being a few months old, with no other tagged releases in the last few years.

[glensc]

The Dockerfile in this repo:

• https://github.com/danger/peril/blob/4c7109895ee956183411a3cb635942825d58bd97/Dockerfile

is not optimized for publishing, it includes development dependencies in the final image layer.