[format-js] ES2015 Module support

[DaleLJefferson]

It seems all of the code mods work with require statements and not import statements, by default (with "add missing Requires") it adds duplicate requires for all of my import statements.

const React = require('React');

import React from 'react';

[johnislarry]

cc @kyldvs who maintains this

[kyldvs]

Yeah this would be a good feature to add behind an option. I maintain this plugin as a side-project, so PRs welcome :)

[zertosh]

And I'd be more than happy to approve it!