[improvement] rename packages dir to src (#3659)

src/sku/constants.js

@@ -0,0 +1,11 @@
+export const LIMIT_TYPE = {
+  QUOTA_LIMIT: 0,
+  STOCK_LIMIT: 1
+};
+
+export const UNSELECTED_SKU_VALUE_ID = '';
+
+export default {
+  LIMIT_TYPE,
+  UNSELECTED_SKU_VALUE_ID
+};