The 'Edit site' link was added to core in [52158], but did not include an icon and was hidden for smaller screen sizes. This change adds the "Appearance" icon to the link and hides the link text when necessary on smaller screen sizes.
Props sabernhardt, desrosj, shaunandrews.
Fixes#54441.
Built from https://develop.svn.wordpress.org/trunk@52209
git-svn-id: http://core.svn.wordpress.org/trunk@51801 1a063a9b-81f0-0310-95a4-ce76da25c4cd
