Add broadcasting

[knmcguire]

Crazyflie-link-cpp can do swarm broadcasting, so why not the link on the cflib!

This is a missing functionality in Crazyswarm2 that blocks the cflib from being a drop in replacement for the cpp backend: IMRCLab/crazyswarm2#423

[NageshEranki]

Hi, this is an enhancement I'm really interested in and would like to see cflib support broadcasting. I'd love to contribute but could really benefit from some pointers.

EDIT 1: I found this old Bitcraze forum thread that was quite informative. I can confirm that the example python script works. Is that post still a good starting point for development?

Thanks