Add the eslint-plugin-testing-librarypackage to our eslint config

[joshblack]

We would like to add support for the testing library ESLint plugin to our eslint config: https://github.com/testing-library/eslint-plugin-testing-library

This issue will cover adding the plugin, enabling relevant rules, and scoping them to specific test files th at are currently using React Testing Library. This will be the tricky part of this change as most files are currently using enzyme. The strategy that we use to bring this in will need to allow us to incrementally update our files over to RTL and the eslint config should be able to reflect that.

[tay1orjones]

It looks like the config was added for this but the dependency was never actually added