Merge pull request #4 from reefactor/fix-build

Fix Var::toDouble() type casting handling & Fix OSX CI github tests by
removing deprecated C API PyUnicode_AsUnicode() for support python 3.12

compile on OSX M1 clang, bump CMake 3.12+

update Catch to v2.13.10 to support modern GCC compilers and M1 hardware