title: React TypeScript: How to type set Props
body: <p>Currently I have to do the following:</p>
  <pre class="lang-js prettyprint-override"><code>interface MyCompProps {
      someAttr: number
  }
  </code></pre>
  <p>I want to use <code>aria-</code>, and then I have to list upfront all <code>aria-*</code> I need. Furthermore, I can't set a simple <code>className</code> on the component. How can I avoid this, i.e. allow normal HTML attributes on component? Or is it a bad practice? I'm skimming the Advanced Guides on reactjs website and nowhere mention that this is a bad practice, so I think it is acceptable.</p>