Update readme

Author: kkarbowiak

README.md

@@ -12,7 +12,7 @@ This is a C++ implementation of Python's `argparse` module. The aim is to cover
 
 ## Dependencies
 
-C++ argparse is a header-only library, so its setup is minimal. It has no external dependencies and only uses STL. Since it uses `std::ranges` and some other features, it requires C++20 compiler and standard library.
+C++ argparse is a header-only library, so its setup is minimal. It has no external dependencies and only uses STL. Since it uses `std::ranges` and some other features, it requires C++23 compiler and standard library. In case of need, [v3.1.0](https://github.com/kkarbowiak/cpp-argparse/releases/tag/v3.1.0) is the latest release that still compiles in C++20 mode.
 
 C++ argparse uses CMake internally, but you don't have to. Just put the [argparse.hpp](https://github.com/kkarbowiak/cpp-argparse/releases/latest/download/argparse.hpp) header somewhere and point your build system to it.