Update README.md

README.md

@@ -55,6 +55,7 @@ To help with the migration, here are the currently known issues with 3.X. This l
 - Shebang URL support for operations is missing.
 - Support for `collectionFormat` is partial.
 - l10n (translations) is not implemented.
+- Relative path support for external files is not implemented.
 
 
 ## CORS Support