adding docstring to recattrs sinks and parsers

[aparna2198]

Added docstrings to three modules as part of improving documentation coverage for the repository.

[Delgan]

Hi.

Thank you for considering improving the docstrings. Loguru would definitely benefit from having more internal functions documented.

Please note that the CI is quite strict and will reject PRs that do not comply with the Ruff linter, in particular, n this case, the rules defined by pydocstyle: https://docs.astral.sh/ruff/rules/#pydocstyle-d
You can validate your changes locally by installing and running pre-commit in your development environment.

Also, be aware that Loguru aims to maintain backward compatibility with Python 3.5. I don't plan on changing that anytime soon, as I want to continue supporting it until the 1.0.0 release. For this reason, unfortunately, you cannot use modern features such as type hints or f-strings.

[aparna2198]

@Delgan I have fixed all the CI issues could you please mark this PR

[Delgan]

Great, thanks for your work on the documentation and for keeping the strict CI happy.

Note that Loguru's public documentation follows the Numpy style. For consistency, I will likely update your docstrings to align with this convention rather than the Google style used in this PR. But this is very fine as it is, the most important thing being the addition of documentation.

[aparna2198]

thanks @Delgan.