Changed rtcIsOpen() return type to bool for consistency

include/rtc/rtc.h

@@ -195,7 +195,7 @@ RTC_EXPORT int rtcSetClosedCallback(int id, rtcClosedCallbackFunc cb);
 RTC_EXPORT int rtcSetErrorCallback(int id, rtcErrorCallbackFunc cb);
 RTC_EXPORT int rtcSetMessageCallback(int id, rtcMessageCallbackFunc cb);
 RTC_EXPORT int rtcSendMessage(int id, const char *data, int size);
-RTC_EXPORT int rtcIsOpen(int id);
+RTC_EXPORT bool rtcIsOpen(int id);
 
 RTC_EXPORT int rtcGetBufferedAmount(int id); // total size buffered to send
 RTC_EXPORT int rtcSetBufferedAmountLowThreshold(int id, int amount);

src/capi.cpp

@@ -675,7 +675,7 @@ int rtcSendMessage(int id, const char *data, int size) {
 	});
 }
 
-int rtcIsOpen(int id) {
+bool rtcIsOpen(int id) {
 	return wrap([id] { return getChannel(id)->isOpen(); });
 }