update readme

Author: lihaoyi

readme.md

@@ -683,6 +683,11 @@ command-line friendly tool.
 - Update all dependencies to latest
 - Support for Scala Native on Scala 3
 
+## 0.2.4
+
+- Backport of *Fix usage of `ParserForClass` for `case class`es with more than
+  22 parameters with some default values in Scala 2.x (#123)* on top of 0.2.3
+
 ## 0.2.3
 
 - Support Scala 3 [#18](https://github.com/com-lihaoyi/mainargs/pull/18)