Add a camera-shutter sound from Kamoso

Copy the sound `kamoso-shutter.wav` from kamoso as `camera-shutter.wav`,
so kamoso doesn't need to provide it any longer (after KF6) and it
becomes themable.

Also added the license CC-BY-3.0 indicated in the source:
https://freesound.org/people/caseymoura/sounds/445482/
which is stated in https://bugs.kde.org/show_bug.cgi?id=402954