Release new minor version

* Pipeline fixes, thx @bryan, @clausen and @caron
* Preparation for conda-forge packaging

- Fix small bug in `__array_ufunc__` when `out` array is not supplied
- Include tests/ in source tarball to enable conda packaging
- Small changes to CI

Small bugfix for matplotlib deprecation (`DivergingNorm` -> `TwoSlopeNorm`)
Not sure if correct Semantic Versioning (patch or minor) due to matplotlib requirement raising to 3.2, though...

Added demos to the documentation.

Fixes and quality of life updates!

3D Plotting and IO

This release contains the `fields` and `vis` subpackage and their respective functionalities.

Fixed bug that mplstyles were not bundled in distribution.

First (visible) try to push to PyPI! NOT a real release yet.