Reformat all docstrings to numpydoc style

[jvavrek]

Files such as isotope_qty.py still use an older docstring style. My VSCode sees this and uses 2 spaces per tab instead of the standard 4. We should update the older files to use the numpydoc style, and @micahfolsom optionally check this automatically e.g. with pre-commit.

[jvavrek]

https://github.com/dadadel/pyment is promising but has some rough edges including introduction of whitespace and introduction of empty docstring fields that will take some manual fixing

[jvavrek]

This would be a good task for an LLM!