Support subtitles in Hudl.FFprobe

[alex6dj]

Hudl.FFprobe was just showing info about video and audio but nothing about incrusted or externals subtitles (ex in multilang mkv file).

TODO: Put some subtites properties in SubtitleStreamMetadata and SubtitleFrameMetadata. But the most important is already in tags (language).

TODO: Implement subtitle and ass filters for hard burn subtitles in video.

TODO: Set [ContainsStream(Type = typeof(SubtitleStream))] to Mp4 container because it supports embedded subtitles (but just like mov_text).

TODO: Implement how to copy as stream a srt subtitle file in mp4 and mkv containers.

- Mp4: ffmpeg -i input.mp4 -f srt -i input.srt -map 0:0 -map 0:1 -map 1:0 -c:v copy -c:a copy -c:s mov_text output.mp4

- Mkv: ffmpeg -i input.mp4 -f srt -i input.srt -map 0:0 -map 0:1 -map 1:0 -c:v copy -c:a copy -c:s srt  output.mkv

Note: In the last two TODO things maybe I fail ;)

[CLAassistant]

All committers have signed the CLA.

[Casey-Bateman]

Is this PR good to go? I see some TODOs left in the title.

[alex6dj]

Not yet a lot of thing to do and to test.