gw-all-fields-template.php: Added filter to customize template content.

[saifsultanc]

Context

⛑️ Ticket(s): https://secure.helpscout.net/conversation/2849211669/78114

Summary

Added filter similar to GPNF's template filter here.

This filter could be utilized as follows:

add_filter( 'gwaft_template_output', function( $content, $slug, $name, $data, $suffixes ) {
    // Modify the content as needed.
    if ( in_array( 'collapsible', $suffixes ) ) {
        $content .= 'whatever we like';
    }
    return $content;
}, 10, 5 );