docs(skills): add migration skill section (#38)

Author: chenjiahan

README.md

@@ -35,6 +35,8 @@ Welcome to try it out and share feedback through issues and discussions!
 
 ## Skills
 
+### Best practice
+
 Rstack CLI is still new and does not have complete documentation yet.
 
 Installing the Rstack CLI skill so the agent can understand how to use it:
@@ -43,6 +45,14 @@ Installing the Rstack CLI skill so the agent can understand how to use it:
 npx skills add rstackjs/rstack-cli --skill rstack-cli-best-practices
 ```
 
+### Migration
+
+Installing the migration skill so the agent can migrate existing projects to Rstack CLI:
+
+```bash
+npx skills add rstackjs/rstack-cli --skill migrate-to-rstack-cli
+```
+
 ## Usage
 
 1. Install `rstack` in your project: