Enforce consistent code style

[OmTheTurtle]

After #835 is merged, it'd be nice to enforce the code style so all our JS / TS code will look and read the same. For this we can use a pre-commit hook with husky and lint-staged so eslint / prettier would run before every commit.
Example package.json config:

	"husky": {
		"hooks": {
			"pre-commit": "lint-staged"
		}
	},
	"lint-staged": {
		"*.{ts,js,json,yml,md}": "prettier --write",
		"*.{ts,js}": "eslint --fix"
	},