chore: use auto-updating theme

Author: rigor789

.vitepress/theme/index.js

@@ -1,5 +1,5 @@
-import Theme from "./vitepress-theme";
-import "./style.css";
+import Theme from "@nativescript/vitepress-theme";
+import "@nativescript/vitepress-theme/theme/style.css";
 
 export default {
   ...Theme(),