Add subtitle list view

[lambdadog]

This is a feature than Language Learning With Netflix has that I'm a big fan of, would definitely love to see it in Subadub as I prefer Firefox for my browsing. It allows easily "looking back" through subtitles without having to scrub the video if, for example, you don't pause in time or something along those lines and can also help give full context for fragments (with part of a sentence in one subtitle, then another in the next) that can often be found in subtitles.