improve definitions for attachments (#20392)

types/asana/index.d.ts

@@ -787,12 +787,13 @@ declare namespace asana {
 
         namespace Attachments {
             interface Type extends Resource {
-                created_at: string;
-                permanent_url: string;
-                download_url: string;
-                view_url: string;
-                host: string;
-                parent: Resource;
+                readonly id: number;
+                readonly created_at: string;
+                readonly download_url: string;
+                readonly view_url: string;
+                readonly name: string;
+                readonly host: string;
+                readonly parent: Resource;
             }
         }