Use qtpy so we can use PySide etc #384

The Qt output widget and toolbar is something I quickly put together because I needed it.

I'd need to add the pyside and qtpy stuff to the qt modules (output and toolbar) here: https://github.com/fastplotlib/fastplotlib/tree/main/fastplotlib%2Flayouts%2F_frame

And here: https://github.com/fastplotlib/fastplotlib/blob/main/fastplotlib%2Flayouts%2F_utils.py#L18