feat(docs): place api references at the end

Author: Char2sGu

docs/src/app/content/core/ng-doc.category.ts

@@ -2,6 +2,7 @@ import { NgDocCategory } from '@ng-doc/core';
 
 const CoreCategory: NgDocCategory = {
   title: 'Core',
+  order: 1,
 };
 
 export default CoreCategory;