Fix links in mobile nav

[Daniel15]

These links are broken on the mobile site layout:

  <nav class="slidingNav">
    <ul>
      
      <li class="navItem">
        <a href="/docs/">Documentation</a>
      </li>
      
      <li class="navItem">
        <a href="/roadmap">Roadmap</a>
      </li>
      
      <li class="navItem">
        <a href="/faq">FAQ</a>
      </li>

They should be /Keyframes/docs/, etc.

Use relative_url so the URLs render properly