'pgrep Xvfb' identifies the process by name, which is a more robust test.

The output of 'ps aux | grep Xvfb' inside the Docker container running on Apple silicon is slightly different
and incompatible with the previous while condition:

$ ps aux | grep Xvfb
root      3025  0.0  0.4 1451928 32588 pts/0   Sl   14:25   0:00 /rosetta/rosetta /usr/bin/Xvfb Xvfb :99 -screen 0 1024x768x16
root      3142  0.0  0.0 1206448 7808 pts/0    S+   14:32   0:00 /rosetta/rosetta /usr/bin/grep grep --color=auto Xvfb

Prevent potential infinite loop if Xvfb is not able to start up, for whatever reason.
Exit with exit code 124 ("Command timed out") after 60 seconds.

One-to-one conversion of the previous Travis CI based testing workflow.
❗️ Currently runs on every push ❗️

A separate Github Action will take care of the package deployment to PyPi.
Therefore, the pip installation within the Docker container can be removed.

'Run tests' should not run on pushed tags, otherwise we it would
get run twice unneccesarily during release tag push.

- Uses PyPA's release Github action.
- The Github repo needs to be set up as a 'Trusted Publisher' on pypi.org.
- ❗️ For testing purposes this workflow currently releases to test.pypi.org ❗️
     → This needs to be removed before a potential merge into main.

Modern twine/build expects long_description to be set.
This way 'README.md' will be displayed on https://pypi.org/project/Qt.py/.

This way it will also render correctly on https://pypi.org/project/Qt.py/.

❗️ Currently references 'martin-chatterjee/Qt.py', for testing purposes. ❗️

❗️ Currently states 'version 1.3.9'. This is an assumption, and
   needs to be changed before merge. ❗️

Test-releases to 'test.pypi.org' as project 'martin-chatterjee-Qt.py'.