Add shutter speed to filename

[felix11h]

In some cases, it would have been helpful to have the shutter speed in the filename. Adding it should not be a problem at all, but how existing files should be updated (if at all) needs more careful consideration.

Possible filename update (matching #22):

OLD: 20240309-1152_x-t3_DSCF7596_2160p-29.97fps.mkv
NEW: 20240309-1152_x-t3_DSCF7596_2160p-29.97fps-SS1-60.mkv

or, alternatively, something like

OLD: 20240309-1152_x-t3_DSCF7596_2160p-29.97fps.mkv
NEW: 20240309-1152_x-t3_DSCF7596_2160p-29.97fps-60sp.mkv