Add a linter and lint config

[Rohit Gohri]

As the project grows, it would be easier to contribute if the project follows a specific javascript style guide.
These are what I use in my personal projects:
Linter: https://github.com/eslint/eslint
Config: https://www.npmjs.com/package/eslint-config-airbnb

But any other would work too

[lucas tostee]

Maybe Prettier too ?

[funny]

prettier added 🙌, lint soon