Add trailing comma to attribute args

Author: jordikroon

phpdotnet/phd/Package/Generic/XHTML.php

@@ -1558,6 +1558,7 @@ private function render_attribute_args(string $args): string {
             } elseif ($part['separator'] === '|') {
                 $prefix = '| ';
             } else {
+                $line .= ',';
                 $prefix = '';
             }
             $lines[] = $line;