Enables binding angular expressions to onsubmit events.
Additionally it prevents the default action (which for form means sending the request to the
server and reloading the current page), but only if the form does not contain `action`,
`data-action`, or `x-action` attributes.
<div class="alert alert-warning">
**Warning:** Be careful not to cause "double-submission" by using both the `ngClick` and
`ngSubmit` handlers together. See the
`form` directive documentation
for a detailed discussion of when `ngSubmit` may be triggered.
</div>