Switch to pyproject.toml and modernize development setup?

[orf]

Hey, Would the project be interested in switching away from the pretty old setup.py environment and instead moving to a pyproject.toml file?

I think also adding pre-commit could be a useful thing. This would mean a setup for a new developer is as simple as:

git clone ...
poetry install
poetry run pytest

If we switch to a lockfile for our dependencies, plus use something like dependabot to get notified whenever a dependency is updated, then we'll be in a good spot for noticing regressions ASAP.

[orf]

I've made https://github.com/fsspec/s3fs/pull/603 as a proof of concept.