Bug 1033465 - [Vertical Homescreen] Cant add pinned sites to a smart collection

https://bugzilla.mozilla.org/show_bug.cgi?id=1033465
Hmm, it may have been possible, seems like that should work. TBH - I think I was just following the style for manifestURLs, which was working. Now looking at it again getting the manifestURLs seems like it needed a promise because of the async callback. Yaay for mixing promises and dom requests I guess.

https://github.com/KevinGrandon/gaia/blob/fcf706730f9db24551a9b436f942ba1ebb9371b6/apps/collection/js/home_icons.js#L46