Add semantic colorization for c++23 #elifdef and #elifndef

[BluTree]

Checklist

• [X] This problem exists even with the setting "C_Cpp.enhancedColorization": "Disabled"

The code with a problem is:

#include <iostream>

int main(int argc, const char ** argv)
{
    #ifdef _WIN32
    std::cout << "Hello World Windows" << std::endl;
    #elifdef __linux__
    std::cout << "Hello World Linux" << std::endl;
    #endif
    return 0;
}

It looks like:

using Material Theme (Community Material Theme Darker)

It should look like:

The #elifdef and #elifndef sould be colored correctly, as this is a supported and standard preprocessor directive from c++23

[jeff-hykin]

man why does the C++ team keep adding junk like this 🙄

anyways, added support in v1.21.1, you should see a huge change in type highlighting as well.