DOC: Documentation should be available for different versions

[Kai-Striega]

Issue with current documentation:

The current documentation shows only for version 1.0

Idea or request for content:

The documentation should show for "dev" and any released versions. This way users can access the documentation for their version.

Take a look at https://pydata-sphinx-theme.readthedocs.io/en/stable/user_guide/version-dropdown.html