Extension:HTML5Tags

Allows a couple of HTML5 tags such as figure/figcaption in wiki code.

This is useful as long as https://bugzilla.wikimedia.org/show_bug.cgi?id=23932 is not resolved.

Allowed tags:
 * article
 * figure
 * figcaption
 * hgroup
 * mark
 * nav
 * section
 * time
 * footer
 * header