setEraser method
void
setEraser()
Switches to eraser mode
Implementation
void setEraser() {
temporaryValue = ScribbleState.erasing(
sketch: value.sketch,
selectedWidth: value.selectedWidth,
scaleFactor: value.scaleFactor,
allowedPointersMode: value.allowedPointersMode,
activePointerIds: value.activePointerIds,
);
}