[ticket/12646] Add data-# attribute to breadcrumb links

https://tracker.phpbb.com/browse/PHPBB3-12646

PHPBB3-12646
`data-forum-id="{navlinks.FORUM_ID}"`
should be replaced with `<!-- IF navlinks.FORUM_ID -->data-forum-id="{navlinks.FORUM_ID}"<!-- ENDIF -->`

or we just add something like:
`<!-- IF navlinks.MICRODATA --> {navlinks.MICRODATA}<!-- ENDIF -->` so extensions can also add `data-album-id="(int)"`