This commit syncs changes for the default theme from its active development repository to core.
This is a follow up to [52081], [52107], [52164], [52222], [52283], [52335], [52375], [52392], and [52430]. It includes fixes to the theme's spacing and adds a search template.
To view the full set of changes, visit 8564fd281f...f0346e1ad2.
Props richtabor, kjellr, danieldudzic, scruffian.
Built from https://develop.svn.wordpress.org/trunk@52555
git-svn-id: http://core.svn.wordpress.org/trunk@52145 1a063a9b-81f0-0310-95a4-ce76da25c4cd
