Add JSDoc for more functions that also relate to the ProductStatistics type.

Address #1638 (comment)

Author: eason9487

js/src/data/actions.js

@@ -889,6 +889,13 @@ export function* receiveMCSetup( mcSetup ) {
 	};
 }
 
+/**
+ * Creates a wp-data action with data payload to be dispatched the received
+ * MC product statistics to wp-data store.
+ *
+ * @param {ProductStatistics} mcProductStatistics The received MC product statistics data.
+ * @yield {Object} The wp-data action with data payload.
+ */
 export function* receiveMCProductStatistics( mcProductStatistics ) {
 	return {
 		type: TYPES.RECEIVE_MC_PRODUCT_STATISTICS,

js/src/data/selectors.js

@@ -129,6 +129,17 @@ export const getMCSetup = ( state ) => {
 	return state.mc_setup;
 };
 
+/**
+ * @typedef {import('.~/data/actions').ProductStatistics } ProductStatistics
+ */
+
+/**
+ * Get the MC product statistics data.
+ *
+ * @param {Object} state The current store state will be injected by `wp.data`.
+ *
+ * @return {ProductStatistics|null} The MC product statistics data. Returns `null` if data have not yet loaded.
+ */
 export const getMCProductStatistics = ( state ) => {
 	return state.mc_product_statistics;
 };