Support more than one icon library at a time

[cnorris-cs]

Per a recent Support conversation, we were informed that Mintlify supports the use of either Lucide or Font Awesome icons with a site, but only one or the other of those. Our needs are larger than what one or the other provides, and there should be able to support the use of both (or more libraries, if they're added later), then just being limited to a single one.