title: When using webvtt in html file, is it possible to change all lines with javascript?
body: <p>I recently created html files with video and webvtt subtitles.</p>
  <p>Everything is fine, but when I watch the video on mobile, the position of the subtitles is too low.</p>
  <p>After searching I found that to fix this I had to add line:XX% to each line of the vtt file.</p>
  <pre><code>00:00:00.000 --&gt; 00:00:03.700 line: 90%
  some subtiltles
  </code></pre>
  <p>The problem is that I have to edit 500+ vtt files of 300+ lines one by one.</p>
  <p>And vtt files will be added in the future.</p>
  <p>I found that css couldn't solve this, so I searched and tried to solve it through javascript, but it didn't work.</p>
  <pre><code>TextTrack.cues.line = number
  </code></pre>
  <p>Is it possible to solve this via javascript?</p>