Integrate SimpleIcons and BrandIcons

[giorgio79]

https://simpleicons.org/

They have npm integration already at https://www.npmjs.com/package/simple-icons

MaterialDesignIcons no longer accepts Brand Icons http://dev.materialdesignicons.com/roadmap/brand-icons

2. BrandIcons
   They already have a Flutter package at https://pub.dev/packages/flutter_brand_icons

Use case

Proposal