Update to fontawesome6?

[Sean1708]

I wanted to use the Bluesky icon from Font Awesome 6, but you can't load both fontawesome5 and fontaweseom6 at the same time so it required me to make changes to the source.

As far as I can tell all icons from 5 are in 6 (though some names have changed, e.g. \faMapMarker => \faLocationPin) and there's the added benefit that 6 includes the \faXTwitter command for the new twitter icon.