Sample with libcamera Signal-Slot approach

[ikevanc]

Thanks for this sample code--it was a huge help in getting started.

Reading the documentation more closely, it seems there is an
implementation of C++ signals and slots in libcamera.

It seems a bit old school to introduce C callbacks and a separate
event loop. One way to maintain C++ state through a C callback is
with the cookie on a request. Messy.

Would you add/modify the example to illustrate the signal/slot approach?
Thank you