Add coverage report and badge on README.md

[luclaurent]

Consider adding test coverage score on README.md using badge. See genbadge, Github Actions (1, 2)

[nennigb]

It is a good idea.

a first local run, yields

Name                                        Stmts   Miss  Cover
---------------------------------------------------------------
amc2moodle/__init__.py                          4      0   100%
amc2moodle/_version.py                          1      0   100%
amc2moodle/amc2moodle/__init__.py               0      0   100%
amc2moodle/amc2moodle/amc2moodle_class.py     163     22    87%
amc2moodle/amc2moodle/convert.py              441     39    91%
amc2moodle/amc2moodle/test.py                 194     13    93%
amc2moodle/moodle2amc/__init__.py               2      0   100%
amc2moodle/moodle2amc/_questions.py           317     37    88%
amc2moodle/moodle2amc/_quiz.py                113      9    92%
amc2moodle/moodle2amc/test.py                  29      2    93%
amc2moodle/utils/__init__.py                    0      0   100%
amc2moodle/utils/calculatedParser.py          224     39    83%
amc2moodle/utils/customLogging.py              79     32    59%
amc2moodle/utils/flatex.py                     56      2    96%
amc2moodle/utils/text.py                       17      0   100%
---------------------------------------------------------------
TOTAL                                        1640    195    88%

which is not too bad. Nonetheless, we also should improve some tests which test only the execution but not the quality of the output eg, test_Elements.
The other missing part is to test the exceptions.

I use Coverage.py:

coverage run --data-file=cov-amc2moodle -m  amc2moodle.amc2moodle.test
coverage run --data-file=cov-moodle2amc -m  amc2moodle.moodle2amc.test
coverage combine cov-amc2moodle cov-moodle2amc 
coverage report

I suggest to do that when we will update the packaging system.

[luclaurent]

Great, we can use coverage.py directly in hatch as package management system: https://hatch.pypa.io/1.13/tutorials/testing/overview/#measuring-code-coverage