Add descriptive message for kit domain restrictions #249
Description
When loading the icon chooser, if the configured kit has domain restrictions that exclude the current domain, the request for pro.min.js (and any other assets) will result in a 403. The icon chooser currently shows a vague failure error message.
But it could and should present a message suggesting that the user add a domain allowance for the current domain in their kit settings in the fontawesome.com account.