[Web] Fix missing RNRenderer export (#6265) (#6266)

## Summary

Fixes #6265 

## Test plan

Applications using reanimated should build properly using bundlers that
use ESM - e.g. Vite.

packages/react-native-reanimated/src/platform-specific/RNRenderer.web.ts

@@ -1,3 +1,4 @@
 'use strict';
 // RNRender is not used for web. An export is still defined to eliminate warnings from bundlers such as esbuild.
-export {};
+const RNRenderer = {};
+export { RNRenderer };