feat(canvas): scaffold module imports and constants

scanslicer/canvas.py

@@ -0,0 +1,10 @@
+from PySide6.QtCore import QPointF, Signal
+from PySide6.QtGui import QColor
+from PySide6.QtWidgets import QWidget
+
+from .canvas_interaction import CanvasInteractionMixin
+from .canvas_render import CanvasRenderMixin
+from .canvas_state import CanvasStateMixin
+
+
+# QtSlicingCanvas: class definition for ScanSlicer behavior.