====== onHold() ======
wrtc.onHold() is an event function called when when call has been put on hold by other end, or retrieved from hold.

It //only// occurs if we have been put on hold by //other end//, not by local [[ixnx:wrtc:js:api:call:putonhold|call.putOnHold()]] and [[ixnx:wrtc:js:api:call:retrievefromhold|call.retrieveFromHold()]].

You can use this event to display call has been put on hold. Audio and voice is muted automatically by wrtc_kit, you do not need to do anything.

===== Arguments =====
wrtc.onHold(obj, hold)
  * obj - call object raising the event
  * hold - boolean:
    * true - call has been put on hold by other end
    * false - call has been retrieved by other end

===== Return value =====
Ignored.