Help/About: WordPress 5.5 About Page.

Speed. Search. Security.

This is the start of the WordPress 5.5 about page. 

Fixes #50416. 
Props ryelle, marybaum, estelaris, yvettesonneveld, michelebutcher-jones, metalandcoffee, melchoyce, marktimemedia, abhanonstopnewsuk, elmastudio, davidbaumwald, audrasjb, afercia, cbringmann, andreamiddleton, desrosj, earnjam, SergeyBiryukov, whyisjake, elrae.

Built from https://develop.svn.wordpress.org/trunk@48675


git-svn-id: https://core.svn.wordpress.org/trunk@48437 1a063a9b-81f0-0310-95a4-ce76da25c4cd