Add typescript-eslint

[charlie-yao]

https://typescript-eslint.io/

• Extends the 3 presets (recommended, recommended-with-types, and strict)
• Add some other misc. typescript-eslint rules (and disable their vanilla ESLint versions)
• Temporarily disable linting for ESLint and webpack config files
  • It'd be nice, but there's some conflicts with tsconfig.json that need to be resolved and it's not important right now
• Minor misc. changes to the codebase to account for the new linting rules