add CMake option to toggle tests (on by default)
add CMake option to toggle tests (on by default)

cppformat/cppformat,lightslife/cppformat,dean0x7d/cppformat,dean0x7d/cppformat,mojoBrendan/fmt,Jopie64/cppformat,cppformat/cppformat,alabuzhev/fmt,wangshijin/cppformat,Jopie64/cppformat,alabuzhev/fmt,cppformat/cppformat,alabuzhev/fmt,lightslife/cppformat,dean0x7d/cppformat,lightslife/cppformat,wangshijin/cppformat,mojoBrendan/fmt,wangshijin/cppformat,mojoBrendan/fmt,Jopie64/cppformat