fix: 🐛 (draghandle) export drag handle directive

Author: nivekcode

projects/ng-sortgrid/src/public-api.ts

@@ -1,6 +1,7 @@
 /*
  * Public API Surface of ng-sortgrid
  */
-export * from './lib/ngsg-item.directive';
 export * from './lib/ngsg.module';
+export * from './lib/ngsg-item.directive';
+export * from './lib/ngsg-drag-handle.directive';
 export * from './lib/shared/ngsg-order-change.model';