Font Awesome Plugin Updated

Hi everyone,

A quick message to say I’ve update my Font Awesome kirbytag for K3.
Plus, now, you can use icons as attribut of (link:…).
Version 2 remains available on the “v2” branch and has also benefited from the new feature for links.

Still v4.7.0 of Font Awesome, because I do not have the utility of the v5, but be feel free to make a pull request.