add workflow for building artifacts

[jimustafa]

Attempts to close #52 and tries to address #29. This PR does several things:

• creates a Makefile for downloading the fonts
• adds instructions in the README for configuring the fonts with fontconfig
• creates a requirements directory for managing (with pip-tools) the dependencies needed to build the artifacts
• creates a workflow for automatically building the artifacts as part of CI/CD
• creates a Makefile in the root directory for running a variety of tasks (eg, building the fonts and figures)

[jimustafa]

This PR may also partially close #32.

[rougier]

Impressive, many thanks. I also need to cleanup scripts because I may have commented some parts in a few of them and I'm not sure all the figures are generated at once. Did you test the workflow locally? Did you encounter any errors with missing figures?

[jimustafa]

Yes, the workflow appears to be working, both locally, and running as a GitHub Action. So far, the cheat sheet is being built, but, yeah, some figures necessary for the handouts are not being generated (specifically, those in scripts/sine.py). Also, it looks like some of the figures should be post-processed with pdfcrop, as suggested by one of your comments in #32.

[lgtm-com]

This pull request introduces 4 alerts and fixes 1 when merging d074da7 into 92d26b5 - view on LGTM.com

new alerts:

• 4 for Variable defined multiple times

fixed alerts:

• 1 for Variable defined multiple times