Support PyTest 8.x

Bump version to 0.1.7

Bump version to 0.1.6

Fix PyTest plugin when xdist is not installed

The pytest_configure_node() hook is only allowed when xdist
is installed. This also updates the tests to run with and
without xdist.

Officially support Python 3.11

Add `py` package as explicit dev dependency

It appears that this was previously a transitive dependency of
one of the other packages installed in the tox environment, but is
no longer (most likely due to the package being deprecated). This
plugin only depends on the package for mypy typing and for backward
compatibility with versions of PyTest prior to 7.0.

Add MANIFEST.in to include README

Publish package README and bump version to 0.1.1

Fix CI publish condition