Clarify that we don't include nor test wifi support and recommend Fedora IoT instead

[travier]

Related to https://github.com/coreos/fedora-coreos-tracker/issues/1575

Proposal: Add a Wifi page in the docs that says:

• How to layer the packages needed for Wifi & firmwares
• Note that we don't test that
• ~~Recommend~~ Mention that Fedora IoT includes those packages by default
• Link to CoreOS layering examples?

Some references from a quick web search:

• https://discussion.fedoraproject.org/t/fedora-coreos-and-wifi/38550
• https://discussion.fedoraproject.org/t/is-there-any-live-iso-with-ignition-and-wifi-support/21707
• https://github.com/coreos/layering-examples/blob/main/wifi/Containerfile

[dustymabe]

• Recommend Fedora IoT

I think we can mention Fedora IoT includes these packages by default and might be better suited for the user's use case, but I would shy away from recommending against FCOS just for that reason.