properly fix #29, restoring PyQt5 support
properly fix #29, restoring PyQt5 support

With PySide6, while QImage no longer has Format_RGB32 and friends in its dir()
(although directly accessing it still works.  We need `dir()` to work, so
we need to properly check for that.  (PyQt5 pretends to have a QImage.Format
which seems to be just QImage.format(), however.)
hmeine/qimage2ndarray,hmeine/qimage2ndarray