Feature Request: Use existing Google Test

[IsaacsLab42]

In my project, I use CPM to download and build Google Test. I have already written numerous unit tests and recently discovered this project. Instead of incorporating Google Test as a submodule, it would be beneficial to have an option to locate and use an existing Google Test. This approach would allow me to manage the version used in my project independently from the version used in this project, thereby avoiding duplicate libraries.