data: Add gears menu ui file.

<?xml version="1.0"?>

<interface>

  <requires lib="gtk+" version="3.12"/>

  <menu id="menu">

    <section>

      <item>

        <attribute name="label" translatable="yes">_Words</attribute>

        <attribute name="action">win.show-words</attribute>

      </item>

    </section>

  </menu>

</interface>