implement suggestions from joss reviewer

[LuisScoccola]

• leading underscore convention for private attributes
• delete unused type attributes
• untrack notebook not used in documentation
• small style improvements
• <3.12 constraint to python version due to numba compatibility

[codecov[bot]]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (9ced70d) 72.64% compared to head (0a76ac7) 72.61%.

:exclamation: Current head 0a76ac7 differs from pull request most recent head 5d63548. Consider uploading reports for the commit 5d63548 to get more accurate results

Files	Patch %	Lines
dreimac/lenscoords.py	0.00%	3 Missing :warning:
dreimac/complexprojectivecoords.py	66.66%	1 Missing :warning:
dreimac/emcoords.py	95.65%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #13 +/- ## ========================================== - Coverage 72.64% 72.61% -0.04% ========================================== Files 10 10 Lines 1053 1048 -5 Branches 189 189 ========================================== - Hits 765 761 -4 + Misses 269 268 -1 Partials 19 19 ```

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