Add CMake

[bensuperpc]

Hello,

I added CMake (It is not based on #197)

• Work with CMake with CMake 3.10 to 3.21 (Recommends 3.17 and above)
• Add git submodule to Find SDL2 and SDL2_image
• Add CMake external project libpcre

You can build and test with these commands (Needs CMake and Ninja-build):

cmake -S . -B build -G Ninja
ninja -C build