Add GNU icon fa-gnu
## Icon

![GNU Logo](https://www.gnu.org/graphics/empowered-by-gnu.svg)

This is a SVG format, so easy to use.

Source file: https://www.gnu.org/graphics/empowered-by-gnu.svg
Source page: http://www.gnu.org/graphics/heckert_gnu.html
License: GFDL 1.3, the Free Art License, or under CC-BY-SA 2.0

## Name Suggestion

fa-gnu

## Use Case

Use for GNU project or symbol of Free Software (ethic and philosophy).



