Core: Add matplotlib backend name for lab 4

In lab 4 the `ipympl.backend_nbagg` backend is called `widget`.

Author: agoscinski

src/scwidgets/cue/_widget_cue_figure.py

@@ -65,7 +65,12 @@ def __init__(
             # we close the figure so the figure is only contained in this widget
             # and not shown using plt.show()
             plt.close(self.figure)
-        elif matplotlib.backends.backend == "module://ipympl.backend_nbagg":
+        elif (
+            matplotlib.backends.backend == "module://ipympl.backend_nbagg"
+            or matplotlib.backends.backend == "widget"
+        ):
+            # jupyter lab 3 uses "module://ipympl.backend_nbagg"
+            # jupyter lab 4 uses "widget"
             with self:
                 self.figure.canvas.show()
         else:
@@ -83,7 +88,12 @@ def clear_display(self, wait=False):
         if matplotlib.backends.backend == "module://matplotlib_inline.backend_inline":
             self.clear_figure()
             self.clear_output(wait=wait)
-        elif matplotlib.backends.backend == "module://ipympl.backend_nbagg":
+        elif (
+            matplotlib.backends.backend == "module://ipympl.backend_nbagg"
+            or matplotlib.backends.backend == "widget"
+        ):
+            # jupyter lab 3 uses "module://ipympl.backend_nbagg"
+            # jupyter lab 4 uses "widget"
             self.clear_figure()
             if not (wait):
                 self.figure.canvas.draw_idle()
@@ -100,7 +110,12 @@ def draw_display(self):
         if matplotlib.backends.backend == "module://matplotlib_inline.backend_inline":
             with self:
                 display(self.figure)
-        elif matplotlib.backends.backend == "module://ipympl.backend_nbagg":
+        elif (
+            matplotlib.backends.backend == "module://ipympl.backend_nbagg"
+            or matplotlib.backends.backend == "widget"
+        ):
+            # jupyter lab 3 uses "module://ipympl.backend_nbagg"
+            # jupyter lab 4 uses "widget"
             self.figure.canvas.draw_idle()
             self.figure.canvas.flush_events()
         else: