✨🐋 Docker support and excluded statuses

[jmleroux]

Easiest dev experience with Docker.

Also add some exclusions for statuses names in order to not fetch GitHub API for useless statuses.

Excluded status is a list of statuses names that we don't want to handle. Managed as an env var to be able to customize it per installation. The list of statuses to excluded are handled as plain strings OR regex pattern

GITHUB_EXCLUDED_STATUSES='["excluded_foo", "excluded_bar", "foo_\w+_bar"]'