[feature] Add support external subtitles

[alexeynl]

I'm looking for solution to live watch torrents but none of existing fits all my requirements.

One of this "must have" feature is availability to choose and play external subtitles.

Many torrent releases contains not only media files in mkv format but also subtitles and sound in external files. These files have the same name as media files so it can be easily mapped such way.

This is example of most popular file structure for such releases:

Example 1.

Title Folder
--Title Name S1 - 01.mkv
--Title Name S1 - 02.mkv
...
--Title Name S1 - 12.mkv
----Subs Subfolder
------Title Name S1 - 01.ass
------Title Name S1 - 02.ass
------Title Name S1 - 03.ass
...
------Title Name S1 - 12.ass
----Sounds Subfolder
------Title Name S1 - 01.mka
------Title Name S1 - 02.mka
------Title Name S1 - 03.mka
...
------Title Name S1 - 12.mka

Example 2.

Title Folder
--Title Name S1 - 01.mkv
--Title Name S1 - 01.ass
--Title Name S1 - 02.mkv
--Title Name S1 - 02.ass
--Title Name S1 - 03.mkv
--Title Name S1 - 03.ass
...
--Title Name S1 - 12.mkv
--Title Name S1 - 12.ass

Real world examples:

Subtitles files in the same directory as mkv:
magnet:?xt=urn:btih:84acb3002b038d699036c0b52d9504ad9e3a960f&dn=Futari%20Solo%20Camp%20%2F%20%D0%A1%D0%BE%D0%BB%D0%BE%20%D0%BA%D0%B5%D0%BC%D0%BF%D0%B8%D0%BD%D0%B3%20%D0%BD%D0%B0%20%D0%B4%D0%B2%D0%BE%D0%B8%D1%85%20%281%E2%80%9421%29&tr=https%3A%2F%2Fbt.animelayer.ru%2Fannounce%3Fpasskey%3D860966ef40252422711b85a7e1d03b93
Subtitles files in subdirs of mkv

Is this possible to add support subtitles placed in external files as described?