Bring in linter to enforce a code style guide

[nchaloult]

To keep our work on this project clean and consistent, I'm proposing that we adhere to a style guide.

This PR includes the following contributions:

• Configure ESLint with Airbnb's Javascript style guide
• Additional ESLint configurations which help React and Typescript to play together nicely
• New lint script in package.json
  • Run $ npm run lint to find and fix any linting errors in .ts and .tsx files

Your code editor can be set up to respect these styling rules and display warnings about them. If you've never used a linter before, but you'd like to give it a shot with this project, we can work together to get it plugged into your dev environment 😃

[ralph-dev]

We are not using Prettier haha ok! This works too I have no preference!

[nchaloult]

I've never heard of Prettier until now. Idk how I missed it it seems huge 🤷‍♀️ Should we bring in Prettier in this PR, or decide to open a new PR if we wanna bring it in later?