This adds a new workflow performing these steps:
- A development docker image is built and pushed to GHCR as
'hedgedoc-ci' labeled with the commit hash
- Tests are run with the image
- If the tests are successful, a production image is built and
pushed to GHCR as 'hedgedoc' labeled with the branch, version tag
if available and the commit hash
At a later time, the built dev image can also be used to run E2E tests
with the other supported databases. Currently, this is not yet possible,
as the database is always expected to run on localhost, not other hosts.
Signed-off-by: David Mehren <git@herrmehren.de>
