Let the user pass -vf options to ffmpeg for things like Deband

[Erfboom]

Is your feature request related to a problem? Please describe.
Color Banding is a byproduct of the software stack and it's being worked on through things like YUV4:4:4 and higher bitrates, but it's still very noticeable in any game that isn't bright and colorful.

Describe the solution you'd like
I don't know if it's possible or feasible, but would it be possible to pass the -vf flag to ffmpeg to apply things like debanding to the video stream on the client side? That would add to the latency depending on how many effects you tack on, but outside of music and rhythm games and fighting games, I'm not sure how much of a real world problem that would actually be.

Describe alternatives you've considered
I tried to use gamescope to apply a deband ReShade effect, but gamescope doesn't handle depth buffer stuff because it needs to read the swapchain from the application which isn't typically provided. Seeing as how moonlight isn't a game and it's only displaying a full screen live stream video, maybe things are different?