Request: Implement deptry / pip-check-reqs

[adamtheturtle]

deptry and pip-check-reqs are similar tools.

They check whether there are unused or missing dependencies.

Use cases include:

• My code works but I rely on a transitive dependency, and that could bite me in the future
• My tests pass, but one of my dependencies is specified as a test dependency
• I am wasting time/space installing a dependency which I do not need

My uninformed guess/hope is that with uv, astral-sh now has the tooling to understand the project's requirements, and with existing ruff rules, there is an understanding of the project's imports.

Context: I took over responsibility for pip-check-reqs a few years ago as a user of the project as it was breaking.