perf(topbar): optimize scroll up/down animation with GPU acceleration

src/components/topbar/topbar.module.css

@@ -52,7 +52,9 @@
   position: fixed;
   width: 100%;
   z-index: 3;
-  transition: top 0.2s ease-in-out;
+  will-change: transform;
+  transform: translateY(0);
+  transition: transform 0.2s ease-in-out;
   align-items: center;
   justify-content: space-around;
 }

src/components/topbar/topbar.tsx

@@ -194,7 +194,7 @@ const TopBarMobile = ({ subplebbitAddress }: { subplebbitAddress: string }) => {
   }, []);
 
   return (
-    <div className={styles.boardNavMobile} id='sticky-menu' style={{ top: visible ? 0 : '-23px' }}>
+    <div className={styles.boardNavMobile} style={{ transform: visible ? 'translateY(0)' : 'translateY(-23px)' }}>
       <div className={styles.boardSelect}>
         <strong>{t('board')}</strong>
         {boardSelect}