[Idea] Bundle the PIXEL_AA shader for scaling pixel art

[eierfrucht]

PIXEL_AA by Shiku is a neat shader allowing for upscaling pixel art from any resolution to any resolution with the result still looking pretty much like proper integer scaling, here's 320x200 (top) upscaled to 1728x1080 (bottom) in cnc-ddraw:

https://i.postimg.cc/fDW6TnF2/pixel-aa-sample.png

Or more broadly, it preserves an (almost) untampered look as if a game were running on a CRT screen at its native resolution.

    Features:
    - Sharp upscaling with anti-aliasing
    - Subpixel upscaling
    - Sharpness can be controlled
    - Gamma correct blending
    - Integer scales result in pixel-perfect scaling
    - Can use bilinear filtering for max. performance