Creates a broadcast channel with the specified buffer capacity.
The resulting channel type depends on the specified capacity parameter:
capacitypositive, but less than UNLIMITED -- creates
ArrayBroadcastChannelwith a buffer of given capacity. Note: this channel looses all items that are send to it until the first subscriber appears;
capacityis BUFFERED -- creates
ArrayBroadcastChannelwith a default capacity.
otherwise -- throws IllegalArgumentException.