Add CMakeLists.txt to the project for configuration

[seclorum]

This PR adds a CMakeLists.txt file to the project, derived from the premake5_v2.lua. The purpose of adding this CMake tooling is to simplify the integration of RIVE with JUCE, which is also being done in this project: https://github.com/seclorum/RIVE4JUCE

The integration of RIVE and JUCE is being discussed in this forum thread:

https://forum.juce.com/t/rive-integration-into-juce8/65768/4

I realize this may be a distraction from mainline RIVE development, however I'm submitting this for others who are working on this integration.

[shikhindahikar]

Hi @seclorum will this CMake file also create build system for the newer Rive runtime repo? I have been trying to build this repo correctly but it is turning out to be pretty frustrating with lack of documentation and inconsistencies.