fix: update items and doc link in readme (#38)

Author: zhu-xiaowei

README.md

@@ -6,7 +6,7 @@ Clickstream Web SDK can help you easily collect and report events from browser t
 
 The SDK relies on the Amplify for JS SDK Core Library and is developed according to the Amplify AnalyticsProvider interface. In addition, we've added features that automatically collect common user events and attributes (e.g., page view, first open) to simplify data collection for users.
 
-Visit our [Documentation site](https://awslabs.github.io/clickstream-analytics-on-aws/en/sdk-manual/web/) to learn more about Clickstream Web SDK.
+Visit our [Documentation site](https://awslabs.github.io/clickstream-analytics-on-aws/en/latest/sdk-manual/web/) to learn more about Clickstream Web SDK.
 
 ## Integrate SDK
 
@@ -105,6 +105,8 @@ It is recommended to set global attributes when initializing the SDK, global att
 
 You can add the following code to log an event with an item.
 
+**Note: Only pipelines from version 1.1+ can handle items with custom attribute.**
+
 ```typescript
 import { ClickstreamAnalytics, Item } from '@aws/clickstream-web';
 
@@ -113,6 +115,7 @@ const itemBook: Item = {
   name: 'Nature',
   category: 'book',
   price: 99,
+  book_publisher: "Nature Research",
 };
 ClickstreamAnalytics.record({
   name: 'view_item',