Is your feature request related to a problem? Please describe...

I use FontAwesome in most of my projects, and being able to keep the icon set I use consistent in my project is important to its UX and Design.

Describe the solution you'd like

I think adding a slot for a custom icon would solve this problem. A prop on the element I think would be less flexable depending on the icon system someone is using.

Describe alternatives you've considered

Right now the only way I would be able to replace the icon is by hiding it via CSS then adding my own SVG icon in its place via CSS. Which seems hacky to me.