Add support for announce and record to server

[gBillal]

Add support for publishing media streams to an RTSP server. In this PR only udp transport is supported. We'll add tcp support in a future PR (it needs some thinking since recording with tcp means receiving rtsp messages will be the responsibility of the handler and not the server anymore).

I'll add later on an example of a PubSub Server where someone is publishing a stream and others streaming it.

[Noarkhh]

Hi @gBillal, could you please push any commit to this branch? I changed our CI config, so that it should trigger on PRs from forks.

[Noarkhh]

Would it be feasible for you to add an example livebook, where the recording functionality is used? The basic_server.livemd example is nice and to have another one that shows how to publish streams to a server would be be nice too.

[gBillal]

@Noarkhh I'm working on an example like that, however it's not as easy as the basic_server.livemd, so I think I'll add it to the membrane_demo repo.

[Noarkhh]

Okay, good to hear :) I'll be waiting for the PR