Add additional marketplace options on launch

doc/marketplace-scripts/checkerboard-test/metadata.json

@@ -0,0 +1,4 @@
+{
+  "name": "Checkerboard test",
+  "description": "Animated checkerboard pattern with a moving offset to spot scaling artifacts."
+}

doc/marketplace-scripts/checkerboard-test/source.js

@@ -0,0 +1,30 @@
+function init() {}
+
+function tick(context, state) {
+    const { ctx, width, height, deltaMs } = context;
+    if (!ctx) {
+        return;
+    }
+    const speed = 0.02;
+    const offset = ((state.offset || 0) + (deltaMs || 0) * speed) % 40;
+    state.offset = offset;
+
+    const squareSize = 40;
+    ctx.clearRect(0, 0, width, height);
+    for (let y = -squareSize; y < height + squareSize; y += squareSize) {
+        for (let x = -squareSize; x < width + squareSize; x += squareSize) {
+            const isDark = ((x + y) / squareSize) % 2 === 0;
+            ctx.fillStyle = isDark ? "#101828" : "#e2e8f0";
+            ctx.fillRect(x + offset, y + offset, squareSize, squareSize);
+        }
+    }
+
+    ctx.strokeStyle = "#ef4444";
+    ctx.lineWidth = 2;
+    ctx.beginPath();
+    ctx.moveTo(width / 2, 0);
+    ctx.lineTo(width / 2, height);
+    ctx.moveTo(0, height / 2);
+    ctx.lineTo(width, height / 2);
+    ctx.stroke();
+}