iFrame `frameborder` attribute is deprecated in HTLM5

[jimblue]

Hi,

First thank for your amazing lib :)

After running a W3C test on the Embera HTML output , I've noticed that the frameborder attribute was deprecated and should be removed: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe#frameborder

The value 1 (the default) draws a border around this frame. The value 0 removes the border around this frame, but you should instead use the CSS property border to control

For now I'm adding a filter to fix that:

$embera->addFilter(static function ($response) use ($loading) {
            if (!empty($response['html'])) {
                $response['html'] = str_replace('frameborder="0"', "", $response['html']);
            }

            return $response;
});

But it would be to release a new Embera for everyone :)