Pull request #17: aterko-WEBRTC-1379-Conference_call_participants_limit

Merge in WEBRTC/infobip-rtc-android from aterko-WEBRTC-1379-Conference_call_participants_limit to master

Squashed commit of the following:

commit 0a78a4a2948811203b171741a3f5f533acbd90ef
Author: aterko <ajsa.terko@infobip.com>
Date:   Fri Mar 19 16:06:41 2021 +0100

    WEBRTC-1379

README.md

@@ -266,6 +266,8 @@ InfobipRTC.registerForActiveConnection(
 
 You can have a conference call with other participants that are also in the same conference room. The conference call will start as soon as at least one participant joins.
 
+Conference call is in the beta stage and available for audio only, with a maximum limit of 12 participants.
+
 Joining the room is done via the [`joinConference`](https://github.com/infobip/infobip-rtc-android/wiki/InfobipRTC#joinConference) method:
 
 ```