Update GLTF KHR_materials_sheen to load roughness

loaders/src/glTF/2.0/Extensions/KHR_materials_sheen.ts

@@ -13,6 +13,7 @@ interface IKHR_materials_sheen {
     intensityFactor: number;
     colorFactor: number[];
     colorIntensityTexture: ITextureInfo;
+    roughnessFactor: number;
 }
 
 /**
@@ -86,6 +87,10 @@ export class KHR_materials_sheen implements IGLTFLoaderExtension {
             }));
         }
 
+        if (properties.roughnessFactor !== undefined) {
+            babylonMaterial.sheen.roughness = properties.roughnessFactor;
+        }
+
         return Promise.all(promises).then(() => { });
     }
 }