Use python-build to also make wheels

[hugovk]

Fixes #237.

Currently, gpxpy is distributed on PyPI only as a sdist:

• https://pypi.org/project/gpxpy/1.5.0/#files

Please could you also distribute a wheel? It makes installation faster. More info:

• https://pythonwheels.com/

This PR updates the makefile to create both an sdist and wheel using https://github.com/pypa/build, and upload both.

This solves another problem too, calling setup.py directly is deprecated by setuptools:

• https://blog.ganssle.io/articles/2021/10/setup-py-deprecated.html

[jtpio]

Thanks @hugovk!

[tkrajina]

Merged, thanks (I plan to clean up a few more pull requests and then release a new version, including your wheel distribution).