Fix colors "works on my machine"

[nokola]

Quick fix to get colors working on Windows - please use as you wish! Ok to close/abandon.

Issue it fixes:

var<private> black_color: vec4<f32> = vec4<f32>(0.15f, 0.15f, 0.21f, 1f);

Expected: Render above shader color as almost black
Actual: renders as light gray

Wrong color example:

Fixed color example:

Also fixed:

[nokola]

For info - I don't know if it will break semi-transparent texture color, haven't tested. Might be OK?

The gist of the change is that render texture/shaders are now considered linear as they are rather than sRGB