fix(turbopack-css): treat css url resolve error as warning (#105)

Author: fireairforce

turbopack/crates/turbopack-css/src/references/url.rs

@@ -79,7 +79,8 @@ impl ModuleReference for UrlAssetReference {
             *self.request,
             ReferenceType::Url(UrlReferenceSubType::CssUrl),
             Some(self.issue_source),
-            false,
+            // Treat as optional so that unresolved URLs emit warnings instead of errors
+            true,
         )
     }
 }