public static function add(string $asset_type, string $asset, string $namespace, int $priority = 1) : void
    {
        Assets::$assets[$namespace][$asset_type][$priority][] = [
            'asset'  => $asset
        ];
    }
public static function add(string $asset_type, string $asset, string $namespace, int $priority = 1) : void
    {
        Assets::$assets[$namespace][$asset_type][$priority][] = [
            'asset'  => $asset
        ];
    }
public static function add ( string $ asset_type , string $ asset , string $ namespace , int $ priority = 1 ) : void { Assets :: $ assets [ $ namespace ] [ $ asset_type ] [ $ priority ] [ ] = [ 'asset' => $ asset ] ; }
Add new asset

Assets::add('js', 'jquery.js', 'site', 1);
Assets::add('js', 'site.js', 'site', 2);
Assets::add('css', 'site.css', 'site', 1);
Assets::add('css', 'theme.css', 'site', 2);

@param  string $asset_type
@param  string $asset
@param  string $namespace
@param  int    $priority
@return void
Add new asset