title: Run a webshim "addCustomValidityRule"
body: <p>I check if one of two text inputs have text, using webshim, and think custom-validity sounds correct.
  <a href="http://afarkas.github.io/webshim/demos/demos/webforms/4-webforms-custom-validity.html" rel="nofollow">http://afarkas.github.io/webshim/demos/demos/webforms/4-webforms-custom-validity.html</a></p>
  
  <p>There is a method called <code>addCustomValidityRule</code> that looks like this:</p>
  
  <pre><code>$.webshims.addCustomValidityRule('testname', function (elem, value) {
      if (value &amp;&amp; $(elem).hasClass('test-class') &amp;&amp; value != 'foo bar baz') {
          return true; //means yes, it's not valid
      } else {
          return false; //no, it is valid
      }
  }, 'you have to enter foo bar baz');
  </code></pre>
  
  <p>But I can't find any way to trigger it. How do I trigger or run it on "submit click"?</p>