chore(docs): add duplicate dependencies plugin

[fengzilong]

Repo: https://github.com/fengzilong/duplicate-dependencies-webpack-plugin

Pros:

• fancy and more detailed report ( size / issuer ... )
  

• rewritten mechanism, so no more extra fs calls

• flexible, it exposes an internal hook named "result" like what html-webpack-plugin did, which will be more extendable

  const DuplicatePlugin = require( 'duplicate-dependencies-webpack-plugin' )
  
  DuplicatePlugin.getHooks( compilation ).result
    .tap( 'duplicates-consumer', duplicates => {
      // do whatever you want with `duplicates`, format / report / write it to disk
    } )