Integrate coverage in GitLab coverage feature
### Todo - [x] The [coverage can reports to the terminal and as htmls altogether](https://pytest-cov.readthedocs.io/en/latest/reporting.html): ``` poetry run pytest --cov silkaj --cov-report html:cov_html --cov-report term ``` - Switch from `pytest-cov` to [`coverage`](https://coverage.readthedocs.io/) dependency?: ```bash poetry run coverage run -m pytest --cov silkaj --cov-report html:cov_html --cov-report term ``` - [x] Then, [specify `coverage` regex](https://forum.gitlab.com/t/python-coverage-always-unknown/47819/3) in [the configuration](https://git.duniter.org/clients/python/silkaj/-/settings/ci_cd#js-general-pipeline-settings) to find it in the logs of the job, to generate the badge and a [chart of the coverage evolution, which is available from GitLab v13.1](https://about.gitlab.com/releases/2020/06/22/gitlab-13-1-released/#graph-code-coverage-changes-over-time-for-a-project). - [x] Remove now useless `coverage-badge` dependency introduced in #146. - [x] Update badge in the readme and the repository configuration
issue