refactor(#637): Migrate testing utilities to Jest pt.1/X

[joeyklee]

Dear ml5 community,

I'm making a Pull Request(PR). Please see the details below.

A good PR 🌟

→ Step 1: Describe your Pull Request 📝

Fixing a Bug? Adding an Update? Submitting a New Feature? Does it introduce a breaking change?

This PR adds the Jest testing framework/library to the ml5-library. This addresses a few elements for me in trying to be intentional about maintainability and approachability of testing for contributors.

I'm advocating for Jest largely because it is both the testing framework (e.g. Mocha or Jasmine) AND the testing assertion library (e.g. Chai) which I think makes it easier to reason about where to look up "how to do X" or "how to mock Y" and helps to create less "stuff" to manage.

It took me ages to finally figure out the differences between Mocha, jasmine, chai, and karma and I found it difficult to understand where the various testing functionalities started and ended. I think I might not be alone on this one!

So! This PR is part of a series of updates that integrates Jest as our testing framework.

I found these blogs helpful for reference:

• https://www.merixstudio.com/blog/mocha-vs-jest/
• https://blog.devgenius.io/the-karma-you-get-for-not-using-jest-e928e7f6b23f

[joeyklee]

Im going to get this process started with the knowledge that there might be some hiccups we'll have to address along the way. Thank you for your patience!