Filters the response from rendering the partials.
Plugins may use this filter to inject
$styles, which are dependencies
for the partials being rendered. The response data will be available to the client via
render-partials-response JS event, so the client can then inject the scripts and
styles into the DOM if they have not already been enqueued there.
If plugins do this, they'll need to take care for any scripts that do
and make sure that these are not injected, or else to override the function to no-op,
or else the page will be destroyed.
Plugins should be aware that
$styles may eventually be included by
default in the response.