[Feature request] Add VHS filter

[ndbiaw]

Rendering the image with SVG makes it look too new to play. I think should add VHS filter to make it look older.

[Difegue]

I don't plan on adding filters, but I've added a basic option to darken the game background to make the SVG rendering pop less.

Another idea was to add a shadow to the SVGs to make them more realistic, but that can't be easily done unless the Avalonia SVG renderer supports transparency.