Twenty Nineteen: Make sure links are followed on touchend, not touchstart.

The theme's original navigation JavaScript was making it so all links on a site were immediately followed on touchstart when using a touch-enabled device. This update makes sure links are followed at touchend, to improve usability and menu behavior.

Already committed to the 5.0 branch in [44357].

Props anevins, panchen, kjellr.
Fixes #45510.


Built from https://develop.svn.wordpress.org/trunk@44358


git-svn-id: https://core.svn.wordpress.org/trunk@44188 1a063a9b-81f0-0310-95a4-ce76da25c4cd