Update [the simple usage example in `README.rst`](https://github.com/EGJ-Moorington/CircuitPython_Button_Handler/blob/ed7e0326fa88e094a21b1bf33b9a5354be97c690/README.rst#usage-example), which has been outdated since version 3.0.0 released.
Update the simple usage example in
README.rst, which has been outdated since version 3.0.0 released.