feat(pr-title): Add empty commit step

[chris3ware]

The required check (enforce-all-checks) will fail if the PR title is invalid - as expected.

enforce-all-checks polls the check api for the most recent commit in the PR. Fixing the PR title does not generate a new commit which means re-running the failed checks workflow still results in failing - because it is polling the previous commit.

In this PR a step will be added to push an empty commit to trigger the checks workflow on a new commit where the PR title check has succeeded.

edit to trigger context output debug

[chris3ware]

The step to push the empty commit is not running because access to the required contexts is not available with the pull_request event; pull_request_target should be used. (According to copilot). I have verified that the context output is empty with the following:

- name: dump pull request event details
run: |
echo "PR action: ${{ github.event.pull_request.action }}"
echo "PR changes: ${{ toJSON(github.event.pull_request.changes) }}"
# Trigger checks with empty commit when PR title is edited to resolve validation failure
- name: Trigger checks with empty commit
if: ${{ github.event.pull_request.action == 'edited' && github.event.pull_request.changes.title.from != null }}
run: |
echo "Title changed from: ${{ github.event.pull_request.changes.title.from }}"

Produces:

Run echo "PR action: "
echo "PR action: "
echo "PR changes: null"