Description:
As per the doc, here and here, setup-python supports built-in caching of pip and pipenv dependencies. It'd nice to have the same feature also for Poetry out-of-the-box.

Justification:
Poetry is one of the latest projects joining the party of Python dependency management systems. If you want to cache inter-run dependencies, you have to build your own caching step (e.g., this):

- name: Set up cache
      uses: actions/cache@v1
      with:
        path: .venv
        key: venv-${{ runner.os }}-${{ steps.full-python-version.outputs.version }}-${{ hashFiles('**/poetry.lock') }}

I'd great if that were managed by setup-python!

Are you willing to submit a PR?
Please, note that I'm not familiar with TS. Looking for support / hints.