Adding CMake-ified, devcontainer-enabled version of ImGuizmo

[aniongithub]

PR for issue https://github.com/CedricGuillemet/ImGuizmo/issues/305

Adding CMake support Using CMake-ified ImGui instead of local copy Switched out windows specific example code for platform-independent SDL2 + OpenGL3 impl code Added VSCode files to enable seamless devcontainer development and a launch.json for the example Removed all binaries from the package

See original PR #306 for previous comments and conversation