Power Draw on Single Transistor Drive Sounders at Idle

[J1mbo]

Thanks for creating and maintaining this library.

It would be useful to be able to specify active-low or active-high drive since many simple passive buzzers use a single PNP transistor for drive. Therefore, as it stands there is un-necessary power draw at idle since the code terminates by setting the output pin low, thereby presenting DC from the transistor supply across the sounder. This also applies to the simplified built-in library.