Add support for uv venvs

[tleonhardt]

Summary

Add support for uv venvs. uv is an extremely fast Python package and project manager, written in Rust. It is a single tool to replace pip, pip-tools, pipx, poetry, pyenv, twine, virtualenv, and more.

uv is an order of magnitude or two faster than pipenv.

Testing

uv venv
uv run inv format
uv run inv lint
uv run inv mypy
uv run inv pytest
uv run inv doc8
uv run inv docs

NOTE: To make my life easy, I edited by .zshrc to add an alias called uinv that maps to uv run inv to run invoke commands using uv in the virtual environment created by uv.

Unrelated

Fix a spelling typo in a unit-test comment