Testing plotnine against `matplotlib` and `pandas`

[isabelizimm]

Adding weekly tests to check plotnine against pypi and latest versions of pandas and matplotlib

Check out actions running on my fork: https://github.com/isabelizimm/plotnine/actions

[codecov[bot]]

Codecov Report

Base: 0.00% // Head: 0.00% // No change to project coverage :thumbsup:

Coverage data is based on head (c8ef278) compared to base (4992e3c). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #631 +/- ## ===================================== Coverage 0.00% 0.00% ===================================== Files 153 153 Lines 10006 10006 ===================================== Misses 10006 10006 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Hassan+Kibirige). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Hassan+Kibirige)

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[isabelizimm]

Ah ha! It is running now on my fork 👍 https://github.com/isabelizimm/plotnine/actions/runs/3283686734

[has2k1]

Great. Thank you. No more being caught unawares.