Show transcript for lectures with subtitles

[carlobortolan]

Motivation and Context

See #1369.

Description

Updated web client to include the option to show lecture transcript with available subtitles.
When the transcript is enabled, the user can read/scroll/fast-forward through the text (see demo video below).

Steps for Testing

Prerequisites:

• 1 Video with subtitles
• 1 Video without subtitles

1. Open a video.
2. a "Show transcript" button should appear if it has subtitles.
3. Now, you should be able to see the transcript next to the video (/ below the video if you're on a mobile device).

Screenshots

2024-11-12.15-04-23.mp4

[github-actions]

Your Testserver will be ready at https://1403.test.live.mm.rbg.tum.de in a few minutes.

Logins

Kurs1	Kurs2	Kurs3	Kurs4
public	public	loggedin	enrolled
prof1	prof1	prof2	prof1 prof2
student1 student2 student3	student1 student2	student2 student3	student1 student2