Chore(demo): Hide elements in Supernova component preview

apps/demo/partials/layout/base.hbs

@@ -46,6 +46,18 @@
         });
         targetElement.classList.add(`theme-${theme}`);
       };
+
+      // Hide elements with hide-from-visual-tests class in Supernova component preview via postMessage
+      // see https://app.supernova.io/8830-alma-spirit/10180-spirit/10368-shared-draft/9731-default/documentation/settings/customization/footer for iframe event listener script
+      window.addEventListener('message', (event) => {
+        // Check if the postMessage is from the Supernova.io domain
+        if (event.origin === 'https://app.supernova.io' && event.data.action === 'hide-from-visual-tests') {
+          const elements = document.querySelectorAll('.hide-from-visual-tests');
+          elements.forEach(element => {
+              element.style.cssText = event.data.style;
+          });
+        }
+      });
     </script>
 
     {{#> scripts}}