Add support for downloading subtitles

[edenman]

trafficstars

Describe the feature you'd like Ability to search for and download subtitles using the OpenSubtitles plugin. This exists in the Expo client but I didn't see it tracked in this project.

[LePips]

Plug-ins are something that I've thought about for implementation but will be very far out.

[farverio]

Just wanted to voice support for this feature as well. Something very helpful that infuse offers and is particularly nice for non native speakers