Cache pip dependencies in github actions

[mogres]

Problem

Closes #249

Solution

Added cache: "pip" to github action workflows that install cellpack dependencies

Type of change

• New feature (non-breaking change which adds functionality)

Steps to Verify:

Checking runtime for github actions, we get a speedup of a few minutes on MacOS and Windows tests

Screenshots:

Before (from PR #247)

After:

[github-actions]

Packing analysis report

Analysis for packing results located at cellpack/tests/outputs/test_spheres/spheresSST

Ingredient name	Encapsulating radius	Average number packed
ext_A	25	236.0

Packing image

Distance analysis

Expected minimum distance: 50.00
Actual minimum distance: 50.01

Ingredient key	Pairwise distance distribution
ext_A

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.75%. Comparing base (6b8a814) to head (c91b8c2).
Report is 1 commits behind head on main.

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Additional details and impacted files

@@           Coverage Diff           @@
##             main     #250   +/-   ##
=======================================
  Coverage   98.75%   98.75%           
=======================================
  Files          19       19           
  Lines         563      563           
=======================================
  Hits          556      556           
  Misses          7        7           

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[rugeli]

We might want to consider upgrading setup.py to pyproject.toml sometime down the line. Otherwise, lgtm!

[mogres]

We might want to consider upgrading setup.py to pyproject.toml sometime down the line. Otherwise, lgtm!

Agreed!

I think a good way to do this is by using PDM to manage dependencies and create a synced pyproject.toml that is stable across operating systems.