Fix feature detection

(HTMLScriptElement.supports is available since the ~ time importmap is supported)

Author: smnandre

ux.symfony.com/templates/base.html.twig

@@ -27,7 +27,7 @@
             </script>
             {% block importmap %}
                 <script>
-                    if (!HTMLScriptElement.supports('importmap')) {
+                    if (!(HTMLScriptElement && HTMLScriptElement.supports?.('importmap'))) {
                         document.head.appendChild(Object.assign(document.createElement("script"),{
                             src:"https://cdn.jsdelivr.net/npm/[email protected]/dist/es-module-shims.min.js",
                             async:true,