* Add GitHub Actions workflow for pull requests

This PR adds a GitHub Actions workflow to run `pytest` on pull requests.

This will help ensure no breaking changes are introduced into the
library.

GitHub Actions is free for public repositories on GitHub.

* try python `3.10`

A zone can be initially created by an alphanumeric fault message.
When created this way, the expander attribute is not marked even
for expander zones.

However, when we receive an expander message, we should update
the zone attribute to be sure it is identified as an expander.

Co-authored-by: AJ Schmidt <ajs4392@gmail.com>

As provided by warthog618 in #54

The restoration based on message.ready is buggy as it iterates over a list it is deleting from.  which results in only half the faulted zones being cleared.  The fix is to iterate over a copy of the list.

* commit initial workflows

* get `setup.py` version from `git`

* fix shared action extensions

* fix action paths/names

* run build/test action before release

* set `fetch_tags: true` on `actions/checkout`

* set `fetch_depth: 0` to get all tag history

* revert testing changes for `release.yaml`

* Revert "fix shared action extensions"

This reverts commit 78235c1.

* add docs

* minor doc updates