fix indexing causing main thread freeze, various polish

quartz/components/MobileOnly.tsx

@@ -0,0 +1,20 @@
+import { QuartzComponent, QuartzComponentConstructor, QuartzComponentProps } from "./types"
+
+export default ((component?: QuartzComponent) => {
+  if (component) {
+    const Component = component
+    function MobileOnly(props: QuartzComponentProps) {
+      return <div class="mobile-only">
+        <Component {...props} />
+      </div>
+    }
+
+    MobileOnly.displayName = component.displayName
+    MobileOnly.afterDOMLoaded = component?.afterDOMLoaded
+    MobileOnly.beforeDOMLoaded = component?.beforeDOMLoaded
+    MobileOnly.css = component?.css
+    return MobileOnly
+  } else {
+    return () => <></>
+  }
+}) satisfies QuartzComponentConstructor