Publish snapshot package on each commit to main branch

[matiasdahl]

• Add GHA to publish snapshot dev-release to PyPI for all commits to main branch

  • See: https://pypi.org/manage/project/pynb-dag-runner-snapshot/releases/

• Part of this PR extracted into other PR (publish main package)

  • Add main branch deployment action #137

Notes on git commit sha:s

As shown below, there are various variables with "the commit sha:s" when running a github action task.

# get-git-commit-shas:

# this will be the merge commit (for PRs) or commit (for commits to a branch)
git --no-pager log --oneline -n 10

# use git
git show --no-patch --format=%H
git show HEAD --no-patch --format=%H
git show <branch name> --no-patch --format=%H


echo "github.sha                         : ${{ github.sha }}"
echo "GITHUB_SHA                         : ${GITHUB_SHA}"

# The below is only defined for GHAs triggered by PR:s
echo "github.event.pull_request.head.sha : ${{ github.event.pull_request.head.sha }}"