Added recommendation opt-out (bug 1072637)
fix `window.performance.now` polyfill (bug 1090572)
improve transitions for hovercat drop-down menu at desktop width (bug 1096654)
Commit from Mozilla Verbatim by user tonnes.mb@gmail.com.: 335 of 335 strings translated (0 fuzzy).
replace isotope (100KB) with salvattore (5KB) for feed layout (bug 1092331)