Add support for passing doubles in HandSignatureControl.toSvg

[joeriddles]

• Add support for passing double values to HandSignatureControl.toSvg

The int values are converted to double values anyways:

hand_signature/lib/src/signature_control.dart

Lines 971 to 975 in 32790cb

	final fitBox =
	bounds.size.scaleToFit(Size(width.toDouble(), height.toDouble()));
	final rect = fit
	? Rect.fromLTWH(0.0, 0.0, fitBox.width, fitBox.height)
	: Rect.fromLTWH(0.0, 0.0, width.toDouble(), height.toDouble());