storeRef(type, obj) {
    if (type === 'texture') {
      this._refs.textures.push(obj)
    } else if (type === 'buffer') {
      this._refs.buffers.push(obj)
    }
  }
Store reference to WebGL texture or buffer on class instance, useful for when we want to delete later

@param {string} type
@param {WebGLTexture|WebGLBuffer} obj