add-filter-comments-by-you feature broken on GHE #1702

GHE is still using a elements instead of li elements all over the place in the UI. Which results in this selector:https://github.com/sindresorhus/refined-github/blob/3737e091b697bf87f0ec4964eb726ab8eaf5ad10/source/features/add-filter-comments-by-you.js#L9 returning a null then the .before call failing.

Selector for GHE will be: .subnav-search-context a:last-child.

Also the markup is different, here is a sample:

<a href="https://<URL>/<org>/<repo>/issues?q=is%3Aopen+mentions%3Abusches+sort%3Aupdated-desc" class="select-menu-item js-navigation-item">
    <div class="select-menu-item-text">
      Everything mentioning you
    </div>
</a>

Note, we're still on GHE 2.14 series and 2.15 is out, if 2.15 has fixed the markup issue then this can be ignored.