We can now reference reusable workflows with local syntax

## What does this mean?
It means we have a way to run tests against changes to shared workflows, by referencing them as "local":
https://github.blog/changelog/2022-01-25-github-actions-reusable-workflows-can-be-referenced-locally/

Basically, just like we do for the actions, we can create workflows in the repo that reference the shared workflows, to run tests against PRs and pushes to the workflows.

## What this does **not** mean
This doesn't solve #4 , because there is still no way to load an action locally from the same repo as a shared workflow, as far as I can tell.

Start with the linked GitHub changelog and inspect the repository's existing workflows. Check how shared workflows are referenced and how PR and push events are handled, while comparing the limitation described in #4. Done means the required local-reference workflow testing behavior is defined and documented or implemented without assuming local actions are supported.

Written by the indexing model from the issue text.