[free-rtc] list config settings

I've configured the following: - anybody can post to the list without being a subscriber (so people can submit their talk proposals) - anybody wanting to subscribe has to be approved If people want to have general discussion, we can refer them to the FSFE list for free-RTC https://lists.fsfe.org/mailman/listinfo/free-rtc and just keep this list for people involved in managing the talks. There are currently four of us on the list: daniel@pocock.pro ralphm@ik.nu saul@ag-projects.com irl@debian.org