Update package.json to set module type and modify vitest.config.ts to use happy-dom environment

Author: hotlong

packages/designer/package.json

@@ -1,6 +1,7 @@
 {
   "name": "@object-ui/designer",
   "version": "0.1.0",
+  "type": "module",
   "license": "MIT",
   "description": "The Tool. A drag-and-drop visual editor to generate Object UI schemas.",
   "main": "dist/index.js",

packages/designer/vitest.config.ts

@@ -1,9 +1,13 @@
 import { defineConfig } from 'vitest/config';
 import path from 'path';
+import { fileURLToPath } from 'url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
 
 export default defineConfig({
   test: {
-    environment: 'jsdom',
+    environment: 'happy-dom',
     exclude: ['**/node_modules/**', '**/dist/**'],
     alias: {
       '@object-ui/core': path.resolve(__dirname, '../core/src/index.ts'),