add support for PyQt6 and PySide6

examples/basic.py

@@ -0,0 +1,14 @@
+from pyqrangeslider import QRangeSlider
+from pyqrangeslider.qtcompat import API_NAME
+from pyqrangeslider.qtcompat.QtWidgets import QApplication
+
+print(API_NAME)
+app = QApplication([])
+
+slider = QRangeSlider()
+slider.setMinimum(0)
+slider.setMaximum(100)
+slider.setValue((20, 80))
+slider.show()
+
+app.exec_()