chore: set up eslint

[hydrosquall]

Motivation

• Previously, we had set up prettier (chore: pre-commit hooks for code style and commit message quality #66 ), but not eslint, despite having eslint mentioned in the package.json. Eslint catches semantic issues that prettier would not detect, so I figured we might as well include it.
• Note that this pr includes commits from chore: set up + document commitizen-cli for authoring clear commit messages #68 , that should be reviewed + merged first.

Changes

• Adds eslint, @typescript-eslint/eslint-plugin, and @typescript-eslint/eslint-plugin

Testing

• This should have no impact on existing code, this is a DX improvement for subsequent updates.

Notes

• The output of yarn run format and yarn run lint can be saved for a follow-up PR.
• yarn run lint prints out a swath of unused variables that can be addressed in a follow-up PR.

[hydrosquall]

Confirmed this is OK to merge in the nteract slack w/ @willingc , as it falls into the category of a minor testing/tooling change.

[github-actions]

🚀 PR was released in v8.2.12 🚀