Help/About: Update the About page for 7.0.

Introducing the new content for the 7.0 About page.

Fixes #64536.
Props mukesh27, audrasjb, jorbin, ankit-k-gupta, parinpanjari, fcoveram, joen, markoserb, Benjamin_Zekavica, westonruter, peterwilsoncc, JeffPaul.



git-svn-id: https://develop.svn.wordpress.org/trunk@62362 602fd350-edb4-49c9-b593-d223f7449a82