Vtt parse fix

[Dananji]

Related issue: #440

The following WebVTT file is displayed in the transcript component with comments:

WEBVTT

region
id:bill
width:40%
lines:3
regionanchor:100%,100%
viewportanchor:90%,90%
scroll:up

STYLE
::cue {
  background-image: linear-gradient(to bottom, dimgray, lightgray);
  color: papayawhip;
}
/* Style blocks cannot use blank lines nor "dash dash greater than" */

NOTE
This file was machine-generated.
The cues and timing maybe not 100% accurate.

1
00:00:01.200 --> 00:00:21.000 region:fred align:left
[music]

NOTE End of music, and starting dialog

2
00:00:22.200 --> 00:00:26.600 region:bill align:right
<em>Just</em> before lunch one day, a puppet show 
was put on at school.

[masaball]

Looks good as far as I can tell