feat: allow setting editorial workflow PR label prefix (#4181)

packages/netlify-cms-lib-util/src/implementation.ts

@@ -89,6 +89,7 @@ export type Config = {
     proxy_url?: string;
     auth_type?: string;
     app_id?: string;
+    cms_label_prefix?: string;
   };
   media_folder: string;
   base_url?: string;