Allow the following URLs to allow the App Store to load through filtering
setup.icloud.com
s.mzstatic.com
phobos.apple.com
deimos3.apple.com
albert.apple.com
gs.apple.com
itunes.apple.com
ax.itunes.apple.com
init.itunes.apple.com
gs-loc.apple.com
New URLS as of March 2018
2.mzstatic.com
p43-caldav.icloud.com
is1.mzstatic.com
is2.mzstatic.com
is3.mzstatic.com
is4.mzstatic.com
is5.mzstatic.com
p43-contacts.icloud.com
p43-bookmarks.icloud.com
p43-fmip.icloud.com
p43-quota.icloud.com
a5.mzstatic.com
a1.mzstatic.com
ocsp.digicert.com