fix: macos "C++20 or later required."

[SamuelScheit]

When trying to build the latest version of the package on macOS it fails with the following error:

/Users/user/Library/Caches/node-gyp/23.5.0/include/node/v8config.h:13:2: error: "C++20 or later required."
   13 | #error "C++20 or later required."
      |  ^

This is caused by the binding.gyp file, which sets the CLANG_CXX_LANGUAGE_STANDARD to c++17

I've fixed it by setting the c++ standard to 20

[dhritzkiv]

Perfect – thank you. This was necessary for nodejs versions > 22, so this is timely for Node 24 support

[dhritzkiv]

Available in v9.0.0-rc.6