docs: add refactoring notice announcement (#247)

Author: alexzhang1030

README.md

@@ -1,3 +1,6 @@
+> [!IMPORTANT]
+> We are heavily refactoring the codebase, so there might only be limited support and a slow response now. The new version will be released soon, if you have any suggestions, please feel free to [create an issue](https://github.com/webfansplz/vite-plugin-vue-devtools/issues/new).
+
 <p align="center">
   <img src="https://github.com/webfansplz/vite-plugin-vue-devtools/raw/main/screenshots/bg.png" />
 </p>