feat: OnNewMaterialAddedObservable notifies its observers

src/Loading/Plugins/babylon.babylonFileLoader.ts

@@ -73,6 +73,7 @@
                     var parsedMaterial = parsedData.materials[index];
                     var mat = Material.Parse(parsedMaterial, scene, rootUrl);
                     container.materials.push(mat);
+                    container.scene.onNewMaterialAddedObservable.notifyObservers(mat);
                     log += (index === 0 ? "\n\tMaterials:" : "");
                     log += "\n\t\t" + mat.toString(fullDetails);
                 }

src/Materials/babylon.material.ts

@@ -789,6 +789,7 @@ module BABYLON {
 
             if (!doNotAdd) {
                 this._scene.materials.push(this);
+                this._scene.onNewMaterialAddedObservable.notifyObservers(this);
             }
         }
 

src/babylon.scene.ts

@@ -3230,6 +3230,7 @@ module BABYLON {
          */
         public addMaterial(newMaterial: Material): void {
             this.materials.push(newMaterial);
+            this.onNewMaterialAddedObservable.notifyObservers(newMesh);
         }
 
         /**