Add babel-plugin-transform-es2015-spread

[cheton]

Webpack throws an error when requiring write-file-webpack-plugin@3.4.1. The generated file didn't transform ...append into ES5 syntax:

dist/index.js

console.log(_chalk2.default.dim('[' + (0, _moment2.default)().format('HH:mm:ss') + '] [write-file-webpack-plugin]'), 
...append);

With ES2015 spread plugin, it will produce correct result like this:

(_console = console).log.apply(_console, [_chalk2.default.dim('[' + (0, _moment2.default)().format('HH:   mm:ss') + '] [write-file-webpack-plugin]')].concat(append));};

[gajus]

https://github.com/gajus/write-file-webpack-plugin/tree/v3.4.2

[YoutacRandS-VA]

#73