Feature clip round 12bit jpeg

[dugalh]

Features:

• Round and clip to dtype range when it is integer.
• Write internal mask when nodata is None.
• Allow 12bit JPEG input / output files.
• Cache RasterArray mask.
• Issue warnings rather than log them.

Fixes:

• Allow --nodata before --dtype on CLI.

Docs:

• Expand CLI 'Output file format' section.
• Add 'Contributing' section.

[codecov[bot]]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (4bbbe1d) 95.80% compared to head (63d0954) 96.12%.

Files	Patch %	Lines
homonim/raster_array.py	93.02%	3 Missing :warning:
homonim/cli.py	93.75%	2 Missing :warning:
homonim/raster_pair.py	90.90%	1 Missing :warning:
homonim/utils.py	66.66%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #3 +/- ## ========================================== + Coverage 95.80% 96.12% +0.32% ========================================== Files 13 13 Lines 1429 1471 +42 ========================================== + Hits 1369 1414 +45 + Misses 60 57 -3 ```

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