Add example images for video artifacts

[FichteFoll]

I was made aware of the fact that we don't have any example image for banding. This needs to be changed.

Also many other artifacts mentioned in https://guide.encode.moe/encoding/video-artifacts.html.

[FichteFoll]

We do have an example for banding in the descale page using Akanesasu Shoujo. I suppose we could use the same image in the recognizing artifacts page.

However, we're also missing examples for several other artifacts, so I'll expand this issue to cover those as well.