QA: Add a code formatter and code linter for standardizing the code style

**Is your feature request related to a problem? Please describe.**
It will be difficult to enforce a coding style as the repo grows bigger and gets more PRs.

**Describe the solution you'd like**
We must use a code formatter (ideally, opinionated one like https://prettier.io/) and a code linter (like https://eslint.org/) to enhance code quality and maintain consistency.