Add is_on property to siren (#63)

zha/application/platforms/siren.py

@@ -113,9 +113,14 @@ def info_object(self) -> SirenEntityInfo:
  def state(self) -> dict[str, Any]:
  """Get the state of the siren."""
  response = super().state
- response["state"] = self._attr_is_on
+ response["state"] = self.is_on
  return response
 
+ @property
+ def is_on(self) -> bool:
+ """Return true if the entity is on."""
+ return self._attr_is_on
+
  async def async_turn_on(self, **kwargs: Any) -> None:
  """Turn on siren."""
  if self._off_listener: