Unmap

Seeing if packaging is irretrievably broken. Python 3.11 taking too long, removed.

- Added `unweave.py`, which contains code to guess the colourmap from an image file or RGB image array.
- Added two notebooks to the docs to illustrate how unweaving works.
- Updated `unmap.unmap()` to guess the colourmap if `cmap=None`.

Testing release

First working release with test and docs.