[Live] Adding an example of a norender model with a button to trigger the render

[weaverryan]

Q	A
Bug fix?	no
New feature?	no
Issues	Fix #1569
License	MIT

[javiereguiluz]

Thanks Ryan!

I like that the new doc addition is concise ... but as a newcomer, I might need something more detailed to understand the reasoning for this and the special action used to trigger the re-render.

If you agree, I'd add the following section after the existing Deferring a Re-Render Until Later section:

Forcing a Re-Render Explictly
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In some cases, you might want to force a component re-render explicitly. For
example, consider a checkout component that provides a coupon input that must
only be used when clicking on the associated "Apply coupon" button:

.. code-block:: html+twig

    <input data-model="norender|coupon">
    <button data-action="live#$render">Apply coupon</button>

The ``norender`` option on the input ensures that the component won't re-render
when this input changes. The ``live#$render`` action is a special built-in action
that triggers a re-render.

[weaverryan]

I like it - thanks Javier!