Subtitles not shown properly

[solimm4sks]

From: libre-tube/LibreTube#4679 (comment)

Example:

Official piped instance:

Youtube.com:

English - Neobrane captions (which are not even available on piped):

[absidue]

The only actually actionable thing here on the NewPipe side is adding support for extracting the json3 subtitle format (seems to have the same information as the srv3 one but with JSON instead of XML). Figuring out how to parse and display those captions is up to LibreTube and Piped.