Declare C++17 as mandatory

[uilianries]

This project is using std::string_view feature, which is from C++17, but is not declared in CMake, neither documented in the README. For who is using latest versions of GCC, clang, ... it should not be a problem, because they already support C++17 as default standard version, but old compiler should break if the standard is not declared explicitly.

[chronoxor]

There is a C++20 enabled in SetCompilerFeatures.cmake

# Choose C++ standard
set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_EXTENSIONS ON)

[uilianries]

@chronoxor Thank you!