Add validation test

tests/validation/config.json

@@ -292,6 +292,11 @@
       "referenceImage": "gltfBuggyDraco.png"
     },
     {
+      "title": "GLTF BoomBox with Unlit Material",
+      "playgroundId": "#GYM97C#2",
+      "referenceImage": "gltfUnlit.png"
+    },
+    {
       "title": "Asset Containers",
       "playgroundId": "#P3U079#19",
       "referenceImage": "assetContainer.png"