chore: tweak spoiler animation

web/src/components/MemoContent/Spoiler.tsx

@@ -10,10 +10,7 @@ const Spoiler: React.FC<Props> = ({ content }: Props) => {
 
   return (
     <span
-      className={classNames(
-        "inline cursor-pointer select-none transition-all",
-        isRevealed ? "bg-gray-100 dark:bg-zinc-700" : "bg-gray-200 dark:bg-zinc-600",
-      )}
+      className={classNames("inline cursor-pointer select-none", isRevealed ? "" : "animate-pulse bg-gray-200 dark:bg-zinc-700")}
       onClick={() => setIsRevealed(!isRevealed)}
     >
       <span className={classNames(isRevealed ? "opacity-100" : "opacity-0")}>{content}</span>