libsrt readme update

Author: markus-perl

README.md

@@ -31,6 +31,7 @@ because I don't have the resources and the time to maintain other systems.
 * `vorbis`: Lossy audio compression format
 * `theora`: Free lossy video compression format
 * `opus`: Lossy audio coding format
+* `srt`: Secure Reliable Transport
 * `nv-codec`: [NVIDIA's GPU accelerated video codecs](https://devblogs.nvidia.com/nvidia-ffmpeg-transcoding-guide/). Installation is triggered only if CUDA installation is detected, follow [these](#Cuda-installation) instructions for installation. Supported codecs in nvcodec:
     * Decoders
         * H264 `h264_cuvid`