doc: mention the plugin in VSCode usage

docs/docs/usage/pep582.md

@@ -69,6 +69,8 @@ Add the following two entries to the top-level dict in `.vscode/settings.json`:
 }
 ```
 
+This file can be auto-generated with plugin [`pdm-vscode`](https://github.com/frostming/pdm-vscode).
+
 [Enable PEP582 globally](#enable-pep-582-globally),
 and make sure VSCode runs using the same user and shell you enabled PEP582 for.