It's been lost during the monorepo migration. Note that building Rust plugins as a subproject is currently broken, https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/issues/171 but I'm going to fix that. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1290>
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/891>
Fix #63