fix: change type of insertBefore to Node for better type safety

src/extensions/customBranding/CustomBrandingApplicationCustomizer.ts

@@ -136,7 +136,7 @@ export default class CustomBrandingApplicationCustomizer
       this.debug('Top rendering failed.', error);
     }
 
-    const insertBefore: ChildNode | null = host.firstChild;
+    const insertBefore: Node = host.firstChild;
     while (staging.firstChild) {
       const element: HTMLElement = staging.firstChild as HTMLElement;
       element.setAttribute('data-custom-branding-owner', COMPONENT_ID);