[7.6.2] YouTube captions in Miteiru, and track preselection

What's New in Miteiru 7.6.2

Changes since v7.6.1.

Features

• The subtitle picker preselects the tracks. The track in the language you're learning goes on top as the primary subtitle, and English goes underneath as the secondary. Mandarin prefers Simplified Chinese, and Cantonese prefers Cantonese or Hong Kong tracks. This works for YouTube captions and for subtitles inside a video file. You can still pick something else.
• More YouTube caption tracks.
  • Auto-generated captions in the video's own language are listed.
  • An English auto-translation is offered when the video has no English track.

Fixes

• YouTube captions load into Miteiru (#98).
  • The picker no longer says "0 YouTube subtitles" when something goes wrong. It says why, for example that yt-dlp wasn't found and where to put it.
  • Tracks with three-letter codes (such as Filipino) are listed.
  • The live-chat replay and duplicate "[Auto]" copies of normal tracks are no longer listed.
  • A video without captions says so.
• YouTube's own captions are switched off when the video plays, so they don't draw over Miteiru's.
• A YouTube caption that only comes as WebVTT now loads instead of failing.
• A stuck yt-dlp now gives up after two minutes instead of leaving the picker loading forever.
• Karaoke lyric lines no longer overlap when they show readings and meanings (#97).

Full Changelog: v7.6.1...v7.6.2