fix: fix missing scaleHelper export

src/index.ts

@@ -1,8 +1,9 @@
 import CalHeatmap from './CalHeatmap';
 import * as constants from './constants';
 import * as positionHelpers from './helpers/PositionHelper';
+import * as scaleHelpers from './helpers/ScaleHelper';
 
-const helpers = { position: positionHelpers };
+const helpers = { position: positionHelpers, scale: scaleHelpers };
 
 export default CalHeatmap;
 export { constants, helpers };