chore: doc about core data structures

Author: SSebo

README.md

@@ -12,6 +12,10 @@ SDK is designed primarily for use in multi-user systems such as web servers and
 
 Reading the short [Basic Terms](https://github.com/FeatureProbe/FeatureProbe/blob/main/BASIC_TERMS.md) will help to understand the code blow more easily.  [中文](https://github.com/FeatureProbe/FeatureProbe/blob/main/BASIC_TERMS_CN.md)
 
+## Core Data Structures
+
+Reading the short [Doc](https://github.com/FeatureProbe/feature-probe-docs/blob/b8c55a35c771e4223469f1b121f8b78ab3d9bc22/docs/sdk/sdk-introduction.md?plain=1#L13-L34) about core data sturtures. [中文](https://github.com/FeatureProbe/feature-probe-docs/blob/b8c55a35c771e4223469f1b121f8b78ab3d9bc22/i18n/zh-CN/docusaurus-plugin-content-docs/current/sdk/sdk-introduction.md?plain=1#L14-L35)
+
 ## Try Out Demo Code
 
 We provide a runnable [demo](https://github.com/FeatureProbe/server-sdk-rust/tree/main/examples) for you to understand how FeatureProbe SDK is used.