Enable Windows build for VS 2019

[syntheticmagus]

At time of writing, the only version of Visual Studio supported by the build instructions is 2017. The only (known) reason for this is the use of OpenCV 3.4 binaries, which are provided with implementations up to, but not beyond, VS 2017, and the CMake package therefore fails if the generator is targeting VS 2019. There are likely a number of viable solutions to this: upgrading OpenCV, building a custom OpenCV install, tweaking the build to simply not fail and link against the older DLL, etc. These options should simply be explored, evaluated, and implemented/documented appropriately to enable the use of newer versions of Visual Studio.