refactor(Pinned posts carousel): Don't animate initial resize (#34868)

app/javascript/mastodon/hooks/usePrevious.ts

@@ -0,0 +1,16 @@
+import { useRef, useEffect } from 'react';
+
+/**
+ * Returns the previous state of the passed in value.
+ * On first render, undefined is returned.
+ */
+
+export function usePrevious<T>(value: T): T | undefined {
+  const ref = useRef<T>();
+
+  useEffect(() => {
+    ref.current = value;
+  }, [value]);
+
+  return ref.current;
+}