Prettier support

[eyesplitter]

Hey!
This pull request allows you to format the codebase and unify it across all developers automatically.
To do that I suppose to use Prettier.
Prettier is an opinionated code formatter

I made a simple config that you can adjust to your needs.

There are two scripts in the package.json

1. prettier - check all files
2. prettier:fix - format all files

You need to make a new PR with prettier:fix to format the whole old codebase
Also, Prettier can integrate with most editors

To see examples check the playground

[akhaneev]

That would be really helpful to have the same automatic formatting preferences for all contributors. It will make the code cleaner and easy to read.