ci: Add snapcraft publish action

[ottnorml]

For this action to work the secrets SNAPCRAFT_STORE_LOGIN must be available.

For the snapcraft publish action to work, the SNAPCRAFT_STORE_LOGIN secret must be available. It can be created as described in the documentation of the action (see link). It should be noted that the name of the secret is different from the one in the documentation to be more readable.

$ snapcraft export-login --snaps=PACKAGE_NAME \
      --acls package_access,package_push,package_update,package_release \
      exported.txt

refs #412, #418

[ottnorml]

I'm not sure how the Snapcraft publishing works for Pomatez, since all channels (latest/stable, latest/candidate, latest/beta, latest/edge) offer the same latest version (see link).

So I decided to use only the stable channel. But this can be easily changed or extendedBut this can be easily changed or extended, like this for example:

release: ${{ startsWith(github.ref, 'refs/tags/') && 'candidate' || 'edge'}}

Taken from https://ubuntu.com/robotics/docs/build-and-publish-a-ros-snap-with-github-actions.

[roldanjr]

I have used the Snapcraft official way of building the Snap package before as you can see here. It triggers when there is a new version released and automatically uploads to the SnapStore but in the edge channel which is ideal then I promote the latest version on the edge to the other channels once I tested it on a Linux machine that it still worked as expected.

But the Snapcraft GitHub integration has been broken and I don't know what happened to why new builds are failing, maybe it is due to some breaking changes on their end that I failed to be updated also, so I decided to remove the integration though I didn't delete the folder yet cause I was thinking it might still be useful for future reference. Right now, I just manually download the snap package here and upload it manually on SnapStore.