Add related project error-class-utils

Author: ehmicky

README.md

@@ -300,6 +300,8 @@ logProcessErrors({ colors: false })
   Create multiple error classes
 - [`error-custom-class`](https://github.com/ehmicky/error-custom-class): Create
   one error class
+- [`error-class-utils`](https://github.com/ehmicky/error-class-utils): Utilities
+  to properly create error classes
 - [`error-serializer`](https://github.com/ehmicky/error-serializer): Convert
   errors to/from plain objects
 - [`normalize-exception`](https://github.com/ehmicky/normalize-exception):