Add doc-stings to all public interfaces.

[xelandernt]

This can make it significantly simpler for users to use the package without having to always reference the documentation,
especially since the documentations is not guaranteed to be up-to-date.

Additionally: Enable the ruff check rule that checks if all public methods have an appropriate doc-string.

[xelandernt]

I kind of before suggested that we use reStructuredText / Sphinx doc strings, but have since noticed that they are extremely verbose compared to something like Google doc strings, perhaps we should switch?

[lesnik512]

@alexanderlazarev0 I agree with switching to other format