Add GitHub Actions installation jobs across environments

[Eve-ning]

Description

As discovered by many during a recent hackathon workshop in SG, we found that many users, (mostly Windows & Mac) faced problems installing through pip / conda.

Furthermore, due to a recent update in pygraphviz, it broke tutorials at that time.

Context

I do find this library's direction good, however, could use more stability, especially when workshops are conducted with it.

Possible Implementation

GitHub Actions (Free) can run pip install / conda install pipelines on many environments.
See: https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners#supported-runners-and-hardware-resources

The workflow may be something like this:

Envs	Windows	Mac	Ubuntu
Installation Method
pip	Job 1	Job 2	...
pip w/ pygraphviz
conda
conda w/ pygraphviz			Job n

Note that dimensionality can be reduced through matrices. Which takes a cartesian product of lists provided.
See: https://docs.github.com/en/actions/using-jobs/using-a-matrix-for-your-jobs

[zzzzzzzzzzzzz]

Hello,

Apologize for a long response. We recently moved to pyviz library to allow fancier visualizations and get rid of pygraphviz which caused this issue.

Also, we have .circleci pipelines to ensure the package works on different platforms.