title: How submit button works without `type="submit"`
body: <p>I'm checking this example in react-hook-form doc: <a href="https://codesandbox.io/s/react-hook-form-v6-controller-qsd8r?file=/src/index.js" rel="nofollow noreferrer">https://codesandbox.io/s/react-hook-form-v6-controller-qsd8r?file=/src/index.js</a></p>
  <p>Weird thing is that the button doesn't have <code>type=&quot;submit&quot;</code>. But it still triggers submit event after clicking. (Screenshot attached below.)
  <a href="https://i.stack.imgur.com/cR2s9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cR2s9.png" alt="enter image description here" /></a></p>
  <p>How does it know which button is the submit button?</p>