Added new presentation video to the documentation

mainpage.dox

@@ -4013,7 +4013,8 @@ ldd janus | grep asan
  *    - Presentation on WebRTC (and Janus) as a way to help musicians at <a href="https://fosdem.org/2021/schedule/event/webrtc_musicians/">FOSDEM 2021</a>;
  *    - Workshop on Janus RTP forwarders (lesson/tutorial) at <a href="https://www.youtube.com/watch?v=uW8ztFCkxVk">ClueCon TGI2021</a>;
  *    - Presentation on Janus and NDI at <a href="https://youtu.be/RZ58vapWfUw?t=1755">ClueCon TGI2021</a>;
- *    - Presentation on Janus and multicast at the <a href="https://youtu.be/cT_74CRBsQs?t=5910">MBONED WG session (IETF 110)</a>. \n\n
+ *    - Presentation on Janus and multicast at the <a href="https://youtu.be/cT_74CRBsQs?t=5910">MBONED WG session (IETF 110)</a>;
+ *    - Presentation on how to use WHIP and Janus for broadcasting at <a href="https://www.youtube.com/watch?v=b_QBd3WnGgY">IIT RTC 2021</a>. \n\n
  *    Apart from these presentations, make sure you also check the slides
  *    and presentations from <a href="https://januscon.it/2019">JanusCon</a>,
  *    the Janus conference we hosted here in Napoli.