pmlmodelling/nctoolkit: v0.9.0

This is a major(ish) release with some breaking changes related to plotting.

On pypi, cartopy has been switched to an optional dependency because it was causing installation difficulties for some users. You can now do a "complete" installation using pip to get all optional dependencies::

$ pip install nctoolkit[complete]

This does not impact the conda version, which will behave as before.

Support is now available for Python 3.11.

File paths with spaces are now supported.