brought back functionality from previous builds but now cross-platform

funnyassets/gfx/ml_quad.metal

@@ -0,0 +1,34 @@
+#include <metal_stdlib>
+using namespace metal;
+
+struct VertexOut {
+    float4 position [[position]];
+    float2 texCoord;
+};
+
+vertex VertexOut vertex_main(uint vertexID [[vertex_id]]) {
+    float2 pos[] = {
+        {-1.0, -1.0},
+        { 1.0, -1.0},
+        {-1.0,  1.0},
+        { 1.0,  1.0},
+    };
+
+    float2 uv[] = {
+        {0.0, 1.0},
+        {1.0, 1.0},
+        {0.0, 0.0},
+        {1.0, 0.0},
+    };
+
+    VertexOut out;
+    out.position = float4(pos[vertexID], 0.0, 1.0);
+    out.texCoord = uv[vertexID];
+    return out;
+}
+
+fragment float4 fragment_main(VertexOut in [[stage_in]],
+                              texture2d<float> tex [[texture(0)]]) {
+    constexpr sampler s(filter::linear);
+    return pow(tex.sample(s, in.texCoord), 0.45f);
+}