Add Turntable camera controller example

[nolankramer]

Sorry for the really late contribution here - it totally got shelved due to conflicting priorities with my own projects and life things.

Currently untested in vsgExamples (but I've tested the controller in my own private project and it works well).

If I get the time I can try to test in a Linux environment at-least. Although it might be awhile until I get a free moment.

[robertosfield]

Thanks for the example. I've merged as a turntable branch:

https://github.com/vsg-dev/vsgExamples/tree/turntable

It builds under Linux without any errors. It runs but I have only been able to translate and zoom in/out, the rotation side isn't working for me yet. I won't have time to investigate right as I lots of other work that needs attending.

[nolankramer]

Found the issue, was using abs() but meant std::abs() when checking rotation angle. Tested as working on Fedora 42.