Add shadcn/ui customization, evaluation, and rules documentation

- Introduced customization and theming guide for shadcn/ui components.
- Added evaluation prompts for creating components with specific requirements.
- Created MCP server documentation for component management.
- Documented API differences between base and radix components.
- Established rules for component composition, forms, icons, and styling.
- Added skills-lock.json to track shadcn skill dependencies.

skills-lock.json

@@ -0,0 +1,11 @@
+{
+  "version": 1,
+  "skills": {
+    "shadcn": {
+      "source": "shadcn/ui",
+      "sourceType": "github",
+      "skillPath": "skills/shadcn/SKILL.md",
+      "computedHash": "80a6226e78f6d1fe464214ae0ef449d49d8ffaa3e7704f011e9b418c678ad4d1"
+    }
+  }
+}