📝 docs(commands): add mini-ui command documentation

- create .roo/commands/mini-ui.md file
- add basic description for mini-ui command: "按小程序ui规范"

.roo/commands/mini-ui.md

@@ -0,0 +1,5 @@
+---
+description: "按小程序ui规范"
+---
+
+按小程序ui规范