fix: export all composables for external packages

- Export all composables to enable custom renderer development
- Allows plotly-renderer and lazy-table-renderer to import required functions
- No circular dependency issues detected after analysis
- Maintains backward compatibility

Resolves import errors for external packages that need useProvidePivotData and providePivotData

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Seungwoo321

src/index.ts

@@ -7,5 +7,7 @@ const Renderer: Record<string, Component> = {
   ...TableRenderer
 }
 
+export * from './composables'
+
 export { VuePivottable, VuePivottableUi, PivotUtilities, Renderer }
 export default { VuePivottable, VuePivottableUi, PivotUtilities, Renderer }