start on a wesl-test cli

[mighdoll]

wesl-test foo.wesl seems handy for users, and potentially for IDE integration.

If foo.wesl contains:

    import lygia::math::saturate::saturate;
    @compute @workgroup_size(1)
    fn foo() { test::results[0] = saturate(1.5); }

the cli could run the test and print the result:

> wesl-test foo.wesl
[1.0]

If foo.wesl contains:

// @toy
@group(0) @binding(0) var<uniform> uniforms: test::Uniforms;

@fragment
fn fs_main(@builtin(position) pos: vec4f) -> @location(0) vec4f {
  let st = pos.xy / uniforms.resolution;
  let color = lygia::generative::snoise::snoise2(...);
  return vec4f(color, 1.0);
}

the cli could run the test and record the image:

> wesl-test foo.wesl -o image.png
created image.png (48Kb)