docs: add migration guide for transitioning from v1.x to v2.x branch

Author: obyalian

README.MD

@@ -149,6 +149,10 @@ Here is the device support list of main branch (v1.x) and v2-main branch (v2.x):
 4. Not supported: we will not support specific device in this version;
 5. To be supported: we will add support in the near future.
 
+**Migration Guide**
+
+If you need to migrate existing projects from the main (v1.x) branch to the v2-main (v2.x) branch, please refer to the official [migration guide](https://orbbec.github.io/OrbbecSDK_ROS2/en/source/7_developer_guide/migration_guide.html)
+
 ## Installation Instructions
 
 Install ROS 2

README_CN.MD

@@ -126,6 +126,10 @@ OrbbecSDK ROS2 Wrapper 提供 Orbbec 相机与 ROS 2 环境的无缝集成，支
 4. 不支持：此版本不会支持该设备；
 5. 即将支持：我们将在近期添加支持。
 
+**迁移指南**
+
+如果您需要将现有项目从 main (v1.x) 分支迁移到 v2-main (v2.x) 分支，请参考官方[迁移指南](https://orbbec.github.io/OrbbecSDK_ROS2/zh/source/7_developer_guide/migration_guide.html)
+
 ## 安装说明
 
 安装 ROS 2