plugins-bad: Enable RIST plugin
plugins-bad: Enable RIST plugin

This plugin has no external dependency and provide an implementation of RIST
simple profile protocol. RIST is derived from RTP, it provides a simple
receiver/transmitter elements that implement restransmission and more frequent
RTCP feedback, making it suitable for internet streaming.

Part-of: <https://gitlab.freedesktop.org/gstreamer/cerbero/-/merge_requests/666>

GStreamer/cerbero,GStreamer/cerbero,GStreamer/cerbero,nirbheek/cerbero,nirbheek/cerbero,GStreamer/cerbero,nirbheek/cerbero,nirbheek/cerbero,GStreamer/cerbero