Update deploy-with-dagster.md

Adding import DltResource in the Definition script.

docs/website/docs/walkthroughs/deploy-a-pipeline/deploy-with-dagster.md

@@ -108,6 +108,8 @@ More details can be found in the article
 
 1. Next, define Dagster definitions as follows:
    ```py
+   import DltResource
+   
    all_assets = load_assets_from_modules([assets])  
    simple_pipeline = define_asset_job(name="simple_pipeline", selection= ['issues_pipeline'])