Fix documentation build system - resolve becca module instance issue

Fixed the issue where multiple becca instances were being created due to inconsistent module import paths. The solution was to export becca from becca_loader and access it from there, ensuring a single instance is used throughout the build process.

Co-authored-by: eliandoran <21236836+eliandoran@users.noreply.github.com>

packages/ckeditor5-math/sample/ckeditor.d.ts

@@ -0,0 +1,7 @@
+declare global {
+    interface Window {
+        editor: ClassicEditor;
+    }
+}
+import { ClassicEditor } from 'ckeditor5';
+import 'ckeditor5/ckeditor5.css';