chore: add example for defaultSort in relations

Author: kasir-barati

documentation/docs/graphql/dtos.mdx

@@ -650,7 +650,15 @@ export class TodoItemDTO {
 ```
 
 :::info
-When we use the `@FilterableRelation` decorator or other [relation decorators](./relations.mdx) you might want to define the default sorting criteria since its default value is `[]`, meaning if you do **not** specify it you will receive the results as your underlying database decided to return it which makes it unreliable.
+When we use the `@Relation` decorator or other [relation decorators](./relations.mdx) you might want to define the default sorting criteria like this:
+```ts title="todo-item.dto.ts"
+import { SortDirection } from '@ptc-org/nestjs-query-core';
+// ...
+@Relation('assignee', () => UserDTO, {
+  defaultSort: [{ field: 'id', direction: SortDirection.ASC }],
+})
+```
+Note that default value for `defaultSort` is `[]`, meaning if you do **not** specify it you will receive the results as your underlying database decided to return it which makes it unreliable.
 :::
 
 ### Allowed Boolean Expressions