Attempt to better support badges w/ GitLab

[dbroemmel]

Checklist

• Code follows the contributing guidelines of the project
• This PR solves an existing issue and provided solution was discussed
• The fix has been locally tested
• Code follows the project's coding standards
• Unit tests covering the new feature have been added
• All existing tests pass
• The documentation has been updated to reflect the new feature

List of related issues or pull requests

• Better support for badges with GitLab #391

Briefly describe the changes made in this pull request

Next to READMEs as source for displayed badges, a GitLab-API call will obtain a list of project badges in case the platform is 'GitLab'. The current badge for howfairis will be compared to badges in both sources for badges, recommendations on what to change/update hopefully cover all combinations.

Two test cases have been amended/extended to cover at least the basics.

Additional Notes

No documentation has been changed, I guess more tests could be added as well.

Instructions to review the pull request

# make a new temporary directory and cd into it
cd $(mktemp -d --tmpdir howfairis.XXXXXX)

# get a copy of the repo
git clone https://github.com/fair-software/howfairis .

# checkout the work from this branch 
git checkout <this branch>

# create a virtual environment named venv3
python3 -m venv venv3

# activate the virtual environment
source venv3/bin/activate

# update pip and friends
python3 -m pip install --upgrade pip wheel setuptools

# install runtime dependencies
python3 -m pip install .

# and, if you need it, the development tools
python3 -m pip install .[dev]

Keep what you need from below, extend as necessary

# run the unit tests
pytest

# tests against a live infrastructure
pytest livetests/