add CN docs

doc/ProductSearch.md

@@ -116,6 +116,8 @@ ProductSearch productSearch = new ProductSearch
                             .build(context);
 ```
 
+For searches in China, please change the endpoint to `https://search.visenze.com.cn`.
+
 ## 3. Solution APIs
 
 There are two main APIs provided in this suite, one allows searching for products based on an image input, the other searches using a product's ID (Recommendations API). A product's ID can be retrieved from a [Search Result](#4-search-results).
@@ -528,6 +530,11 @@ ProductSeach productSearch = SearchAPI.getProductSearchInstance();
 Tracker tracker = productSearch.newTracker();
 ```
 
+For China, please change the tracker to:
+```
+Tracker tracker = productSearch.newTracker(true);
+```
+
 ### 7.2 Send Events
 
 Currently we support the following event actions: `click`, `view`, `product_click`, `product_view`, `add_to_cart`, and `transaction`. The `action` parameter can be an arbitrary string and custom events can be sent.

visearch-android/src/main/java/com/visenze/visearch/android/ProductSearch.java

@@ -101,6 +101,10 @@ public Tracker newTracker() {
         return newTracker(null, false);
     }
 
+    public Tracker newTracker(boolean useCnEndpoint) {
+        return newTracker(null, useCnEndpoint);
+    }
+
     public Tracker newTracker(String code) {
         return newTracker(code, false);
     }