In current version, the create_baseline_stubs.py script defaults to the project name as the package name. This is not always the best choice (e.g. PyYAML and yaml), and the --package can be used in that case.

In this PR, I'm improving the default package detection when there is no --package flag. Because this script is run manually, I feel like it is ok to display a message saying to use --package flag if the detected package is not the wanted one.

I checked with the following projects:

• redis defaults to redis
• python-nmap defaults to nmap
• PyYAML defaults to yaml (note that PyYAML also exports a _yaml module)

The improvement relies on importlib.metadata module, and fallbacks to current default (i.e. project name) if that fails or for Python < 3.8 (where that module does not exist).

The code for package detection is slightly inspired by packages_distributions in Python >= 3.10.