Adding self-query code for blog

[Jsasres]

Adding the code, readme, and requirements for the upcoming blog on self-querying retrievers

[JessicaGarson]

This seems to be failing a check on our end, @Jsasres. Have you run the pre-commit check like so:

 python -m venv .venv
.venv/bin/pip install -qqq -r requirements-dev.txt
.venv/bin/pre-commit install

[Jsasres]

@JessicaGarson Sorry just to clarify am I running this pre-commit check in my IDE environment or within git? I did all of this via the Github Mac app so I don't know if that changes anything