easy and robust cmake build process.

[liudeyuan2021]

I use MacBook m1 when I learn the Vulkan tutorial, I can't install stb or tinyobjloader through homebrew, so I have some problems when I build the files the first time.

I change the CMakeLists.txt and add stb and tinyobjloader submodules. I think it will be easier for someone who isn't familiar with CMake to build the files.

[Overv]

While I appreciate the effort, I don't think it's a good idea to add git submodules for the dependencies because it clutters the repo a bit too much. Perhaps someone else with Mac experience can chime in on how the installation process could be made easier.

[SaschaWillems]

An alternative to having submodules would be using FetchContent to download the dependencies at runtime.

Having cmake setup that works out of the box would be very much appreciated btw. ;)