Support pixelated assets

[yopox]

Is your feature request related to a problem? Please describe.

Itch is the home for a lot of indie developers using pixel art, and after working hard on a project it is really frustrating to see our art/screenshots blurred. As an example, when I open itch.io homepage I can count 33 cover images out of 79 using pixel art that would benefit from pixelated rendering.

image-rendering: pixelated is available on all browsers (the last one being Firefox in late 2021), so it is possible to make the situation better.

Related issues:

• Feature Request - Avatar image resample setting, or manual upload of different sizes used. #981
• Bug: blurry cover images for projects of type book #1322
• https://itch.io/t/770231/blurry-pixel-art-on-profile-pic

Describe the solution you'd like

• Have a way to control whether custom filtering is applied on uploading an asset (I guess Support webp image format for screenshots and other images #1609) would solve this point).
• Have a way to control whether an asset should get image-rendering: pixelated (for instance naming assets *.pixelated.webp).

Describe alternatives you've considered

I have custom CSS support on my account, it works for images in game descriptions. However screenshots, cover images and avatars are compressed after the upload so applying a custom image-rendering with CSS looks bad.