Feature Request: Add PA (Public Announcement) On/Off #11

Hi,

pymonoprice can read PA status via zone_status.pa, but there’s no method to turn PA on or off programmatically.

Use case: automating announcements in Home Assistant or other systems.

Suggested addition: a method like

def set_pa(self, zone: int, enabled: bool) -> None

that sends <10PA01\r> / <10PA00\r> over the existing connection.

This would allow full PA control, complementing the existing status reading.

Thanks!