WEBVTT - Chapters for sample-720p-h264-aac.mp4

NOTE Free sample WebVTT chapters track from
99helpers.com/file-types/vtt. Load it with kind="chapters".
Each cue is one chapter: its text is the title. Chapter cues
must not overlap.

chapter-1
00:00:00.000 --> 00:00:04.000
Introduction and test tone

chapter-2
00:00:04.000 --> 00:00:07.000
Colour bars and the beep

chapter-3
00:00:07.000 --> 00:00:10.000
Frame counter and the end