Migrated to JavaScript Standard Style

Changed CI config
Implemented ESLint
I led an incremental migration to Standard JS! We wanted a way to migrate our codebase to Standard incrementally, so that our engineers could learn the new code style over the course of a few weeks. I read through the Standard source code, figured out what rules they use with ESLint, and incrementally migrated our codebase over the course of 1-2 months. I also added a pre-commit hook to lint staged files, and modified our CI status to lint code using both our current config and the config changes on any branch.