download srt: use netflix API to construct filename

[cyphar]

Recently, Netflix stopped making the name of the current video easily available, resulting in every downloaded file using the video ID as a filename.

Luckily we can construct a filename using the Netflix API and the video ID. This has the benefit of being consistent across all languages and types of media, though this might be a downside if a particular language has a very different way of representing show seasons and episodes.

Fixes #32 Fixes #33 Suggested-by: @MinmoTech Signed-off-by: Aleksa Sarai [email protected]