docs: add missing class doc strings for rpc-enabled widgets

bec_widgets/widgets/control/device_control/position_indicator/position_indicator.py

@@ -8,6 +8,10 @@ from bec_widgets.utils.colors import get_accent_colors, get_theme_palette
 
 
 class PositionIndicator(BECWidget, QWidget):
+    """
+    Display a position within a defined range, e.g. motor limits.
+    """
+
     USER_ACCESS = ["set_value", "set_range", "vertical", "indicator_width", "rounded_corners"]
     PLUGIN = True
     ICON_NAME = "horizontal_distribute"

bec_widgets/widgets/control/scan_control/scan_control.py

@@ -41,6 +41,10 @@ class ScanControlConfig(ConnectionConfig):
 
 
 class ScanControl(BECWidget, QWidget):
+    """
+    Widget to submit new scans to the queue.
+    """
+
     PLUGIN = True
     ICON_NAME = "tune"
     ARG_BOX_POSITION: int = 2