ci: add unit tests & release workflows

[hbollon]

I added two CI workflows:

• Test one: which execute build + unit tests on every push on master branch and on PR
• Release one: which Relase a new Docker release on GHCR for rvery tags pushed on the format [0-9]+.[0-9]+.[0-9]+

A dummy package was pushed on the GHCR repo for testing purposes 0.0.1

[hbollon]

I added a Dependabot configuration which will do security updates and also normal flower dependencies updates (once a week, every monday).
I also added a workflow which will automatically approve and merge (rebase method) these PRs.

[hbollon]

Both test and release workflows was tested on my feature branch and this PR.
However Dependabot config and auto-merge workflow cannot be test until this PR is merged unfortunately