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/postcss.config.js

@@ -1,4 +1,4 @@
-module.exports = {
+export default {
   plugins: {
     tailwindcss: {},
     autoprefixer: {},