vectorio import should be optional inside the widget module

[FoamyGuy]

Currently the import here:

Adafruit_CircuitPython_DisplayIO_Layout/adafruit_displayio_layout/widgets/__init__.py

Line 10 in f9438d2

import vectorio

makes vectorio a hard requirement for anything inside of the widgets module within this library.

If I understand correctly the vecotorio import is only used if something calls rectangle_helper() which is also in this file. Wrapping this import with try/except would allow the module to be used in contexts where vectorio is not present i.e. using objects that extend widget.Widget with Blinka_Displayio (as long as those widgets don't need rectangle_helper() or anything else from vectorio specifically.