Ease of comparison (FSR Sample)

[MahadAdnanGul]

While working on finding ways to improve the quality of FSR upscaling techniques, I found it quite inconvenient to use the mouse to swap between upscaling modes as I would have to take my eyes off the part of the image I was focusing on to make comparisons.

I think having key bindings for swapping between upscaling modes would be a small but much needed feature to help contributors in improving FSR.