Add WebVTT support
Depends on GStreamer supporting (at least a bit) VTT files: https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/issues/600
Edited by Bastien Nocera
Depends on GStreamer supporting (at least a bit) VTT files: https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/issues/600