Start UI testing

[joshuaharry]

Pull request type

Please check the type of change your PR introduces:

• [ ] Bugfix
• [ ] Feature
• [X] Other (please describe):

Here we set up the infrastructure required to start writing basic UI tests. This includes a very simple "Hello, world!" check which makes sure the application doesn't crash when we try to render it.

Pull request checklist

Please check if your PR fulfills the following requirements:

• [ ] If it's a backend change, tests for the changes have been added and go test ./... runs successfully from the root folder.
• [X] If it's a frontend change, Prettier has been run
• [X] Docs have been reviewed and added / updated if needed

What is the current behavior?

There are no tests for the UI.

What is the new behavior?

You can now run:

npm test --prefix dashboard

And see the tests pass, albeit with lots of warnings. We'll probably need to do some cleanup later.

Technical Spec/Implementation Notes

We're using jest and react-testing-library to kick things off with unit testing. There are a number of other practices we'll want to implement as we go; the idea here is to start with a small, simple improvement with a lot of value. (I've avoided accidentally bricking production a couple times thanks to tests like this one!)

[jusrhee]

dashboard/package-lock.json conflicts need resolving