bump C++ version to C++20

Author: glesur

CMakeLists.txt

@@ -2,7 +2,7 @@ cmake_minimum_required(VERSION 3.16)
 if (NOT CMAKE_BUILD_TYPE)
     set(CMAKE_BUILD_TYPE "Release" CACHE STRING "" FORCE)
 endif()
-set (CMAKE_CXX_STANDARD 17)
+set (CMAKE_CXX_STANDARD 20)
 
 set(Idefix_VERSION_MAJOR 2)
 set(Idefix_VERSION_MINOR 2)