Switching API to use type="module" scripts

This allows using imports inside scripts imported by WorkAdventure out of the box (and therefore easily importing the scripting-api-extra without resorting to using a bundler)

front/dist/iframe.html

@@ -11,6 +11,7 @@
         const scriptUrl = urlParams.get('script');
         const script = document.createElement('script');
         script.src = scriptUrl;
+        script.type = "module";
         document.head.append(script);
     </script>
     </head>

front/src/Api/IframeListener.ts

@@ -326,7 +326,7 @@ class IframeListener {
                     "//" +
                     window.location.host +
                     '/iframe_api.js" ></script>\n' +
-                    '<script src="' +
+                    '<script type="module" src="' +
                     scriptUrl +
                     '" ></script>\n' +
                     "<title></title>\n" +