Enhancement: Add Docker Hub image (#965)

* Enhancement: Add Docker Hub image

* Push to ghcr.io

* Add all `org.opencontainers.image.xxx` labels using `--label` instead of `LABEL`

* Change `php-fpm` to listen on `:9000` to expose prometheus metrics via `php-fpm_exporter`

* Include `yarn.lock` to speed up builds

* Reorder

* Use correct sha for pr

* Add logging before overriding values in config

* Add `DEBUG=true` env var for verbose `entrypoint.sh` logs

* Print php exception when snappymail fails to generate data directory and config file on the very first time

* Log snappymail version

* Fix COPY statement

* Add .dockerignore

* Add `USER` and `ENTRYPOINT`

* Update `.dockerignore`

* Add docker image test

* Push only if image test succeeds

* Log when startup is successful

* Use plain `docker build` in `build_and_test.sh`

* Fix test output

README.md

@@ -5,6 +5,10 @@
   <br>
   <h1>SnappyMail</h1>
   <br>
+
+[![github-actions](https://github.com/the-djmaze/snappymail/workflows/ci/badge.svg)](https://github.com/the-djmaze/snappymail/actions)
+[![docker-image-size](https://img.shields.io/docker/image-size/the-djmaze/snappymail/master)](https://hub.docker.com/r/the-djmaze/snappymail)
+
   <p>
     Simple, modern, lightweight &amp; fast web-based email client.
   </p>