Add [data-formbuilder] and Psr15DialogFormResponse

[dtdesign]

This PR allows fully automated handling of PSR-15 based form builder dialogs with support for redirects and page reloads. Adding the data-formbuilder attribute in combination with data-endpoint on a button-like element will enable the automated click handling, eventually invoking the PSR-15 dialog form.

<button data-formbuilder data-endpoint="{$endpointUrl}">Click me</button>

The PHP endpoint can utilize the Psr15DialogFormResponse to redirect(string $url) or reload() the page.

return Psr15DialogFormResponse::redirect($someUrl)->toResponse();

The client implementation will trigger the formBuilder:result event on success, providing the response data using the detail property of the event. This event can be cancelled with .preventDefault() which will prevent the aforementioned redirect() or reload() taking place.