mediawiki.html: Fix jsduck syntax for list, backtick html, link url

mediawiki.html: Fix jsduck syntax for list, backtick html, link url

* For the list to render as a list (instead of a paragraph
  with hyphens in it and collapsed linebreak whitespace), it has
  to be in block context. Meaning, a line break first.

* Backtick the <br> tag, otherwise it becomes an actual line
  break as Markdown supports <br>.

* Turn the url into an actual link (unlike wikitext, Markdown
  doesn't do magic linking of urls).

Change-Id: I0e3913cd5f97bf37381a99cbdc6af651a8872c70