Add option to use "sid=" value from mpv.conf inside media folder

[soredake]

MPV has useful option for overriding certain options per-folder by creating mpv.conf in it with option you need (for example sid=2 to always select subtitle number two), but, sub-select overrides mpv's subtitle selecting logic and "sid" value from this file is not used, so, it would be nice to have an option to use "sid" value if mpv.conf has it.

[CogentRedTester]

Can you try the file from the commit referenced above.

[soredake]

Thank you! After switching to this branch and enabling force_prediction sid option is now respected in mpv.conf