I needed to make a few big changes to add JS testing. Additionally, this PR includes many tweaks to the documentation - so feedback is much appreciated 😄

Summary of Changes

1. By far the biggest change is that I moved the JS dependencies we currently have (jquery, moment.js, Chart.js, d3.js) into this repo. I needed to do this so that the test runner is able to load them into our target JS environments (Chrome, in our case, but potentially we could add more in the future), since the main charts.js source file we author directly depends on them and assumes they are available globally.
   • If y'all don't like this change, I can look into seeing how viable mocking out all our JS dependencies would be. However, I expect this to be a tedious task, and if we ever add new JS dependencies (or update existing ones), we'd have to also update the mocks. 😒
2. Tweaked CONTRIBUTING.md documentation to explain where to look for info on how to validate (i.e. run the tests) the web app component.
3. Clarified the Getting Started section of the top-level README.md to explain what the updater and docs subdirectory / components are and linking to their relevant READMEs.
4. Added a README.md to the docs/ component, explaining (in so far as I understand) how the web app works, how it is structured, and how to run tests (and in the hopefully-near-future, linter).
5. Tweaked jekyll _config.yml to exclude the extra node.js bits, like dependency directory and config files.
6. Added basic smoke tests for charts.js - nothing more than checking for the existence of our main createChart functions. Hopefully, with every bug we identify therein, or with every new JS feature we add, we can also add tests now.

Try It Out

Ensure you have Google Chrome installed (and updated). Ensure you have a recent version of node.js available. Pull this branch down, then:

$ cd docs
$ npm install # install dependencies
$ npm test # should exit with code 0 and print out friendly green text saying 4 tests passed

Want to see what a failing test looks like? Edit docs/spec/charts.js, and inside one of the test blocks (encapsulated via the it() function), add expect(false).toBe(true); - then rerun the tests via npm test. Oh no! Angry red text and error stack traces everywhere!