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/scripts/copy-tinymce.js

@@ -1,5 +1,10 @@
-const fs = require('fs');
-const path = require('path');
+import fs from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'url';
+
+// Get __dirname equivalent for ES modules
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
 
 // Create the directory if it doesn't exist
 const targetDir = path.join(__dirname, '..', 'public', 'tinymce');