refactor(config): migrate configuration files to ES module syntax

- Updated jest.config.js, postcss.config.js, and tailwind.config.js to use ES module export syntax.
- Added "type": "module" to package.json to support ES module imports.
- Refactored copy-tinymce.js to utilize ES module imports and defined __dirname for compatibility.

worklenz-frontend/package.json

@@ -2,6 +2,7 @@
   "name": "worklenz",
   "version": "1.0.0",
   "private": true,
+  "type": "module",
   "scripts": {
     "start": "vite",
     "prebuild": "node scripts/copy-tinymce.js",