_addToParent(texture, source, sourceType) {
        this._addSourceToParent(source, sourceType);

        // add the texture to the parent
        this._parent && texture.addParent(this._parent);
    }
Adds the loader parent to the newly created texture
     Also adds the source to the correct parent assets array

     params:
     @texture (Texture class object): our newly created texture
     @source (html element): html image, video or canvas element that has been loaded
     @sourceType (string): either "image", "video" or "canvas"
*