Migrate to JupyterBook

[HuwCheston]

Fixes #72 (?)

This PR migrates entirely to JupyterBook. This has a number of benefits:

• much nicer presentation
• I've configured easy, one-click access to launch a notebook with provisioned compute in either Colab, Binder, or directly on the website with Thebe
  • Thebe/Binder use a custom environment with pinned dependencies, which should eliminate the problems with packages on Colab becoming out-of-date over time

Note that this build may not work entirely "out-of-the-box", we'll probably need to play around with the github actions + pages configuration once it's merged.

For a preview, you can check out how this PR looks on my own fork:

https://huwcheston.github.io/musicinformationretrieval.com/intro.html

[iranroman]

let's also say "or send us an email"

[HuwCheston]

Would maybe prefer sticking just to "create an issue", although it may be a bit tech-y. I feel like hardcoding email addresses isn't the best long-term solution, there's no guarantee that either of us will continue maintaining this site in the future -- we might hand it over to somebody else in the community.

[HuwCheston]

@iranroman, I've pushed (many) commits today that do the following:

• fixed broken dependencies
• optimized all imports with isort
• ran black formatting over all notebooks
• added action to makefile for running black (make fix)
• added action to makefile for running jupyter-book to build HTML
• added many many more tests for formatting (e.g., checking titles, checking for empty cells, checking for import mirdotcom etc.)
• add get_audio func to mirdotcom.py, lets us replace all ../../assets/audio/some_audio.wav with get_audio("some_audio.wav"). Note that librosa.load` is maintained so we're not doing too much "under the hood"
• add list_audio func to mirdotcom.py, replaces all calls of !ls ../../assets/audio
• removed "hide-input" tags
• labelled all y-axis figures
• removed function names from titles of sections
• added missing closing parenthesis to spectral_features.ipynb
• added beginner tutorial to python_basics.ipynb
• moved "People who use this site" to other.ipynb
• added mention that "we welcome .ipynb files" to intro.md in place of mentioning Colab
• fix YouTube video in sheet_music_representations.ipynb
• fix closing parenthesis in sheet_music_representations.ipynb
• fix broken markdown formatting in midi_conversion_table.ipynb

The remaining issues you mention have been converted to these issues:
#74 #75 #76

[iranroman]

Thanks @HuwCheston
This is excellent.