Find a way how to publish non-official pygeodiff versions

[MarcelGeo]

We need to publish experimental versions of pygeodiff:

• using pip versioning
• using new pip distro

[wonder-sk]

It seems like the easiest option would be to do a pre-release (https://peps.python.org/pep-0440/#pre-releases). The version will have alpha/beta suffix (e.g. 3.0a1). The ordinary pip install pygeodiff should skip it, but it will be possible to install either through direct version spec (pip install pygeodiff==3.0a1) or by allowing pre-releases (pip install --pre pygeodiff)