chore: add changeset

Author: piecyk

.changeset/angry-poets-visit.md

@@ -0,0 +1,10 @@
+---
+"@tanstack/react-virtual": patch
+---
+
+feat(react-virtual): add `useFlushSync` option
+
+Adds a React-specific `useFlushSync` option to control whether `flushSync` is used for synchronous scroll correction during measurement.
+
+The default behavior remains unchanged (`useFlushSync: true`) to preserve the best scrolling experience. 
+Disabling it avoids the React 19 warning about calling `flushSync` during render, at the cost of potentially increased visible whitespace during fast scrolling with dynamically sized items.