Yt link button in pdf

[zenithexe]

PR Fixes:

• 1 Converts the static Youtube Video thumbnails in pdfs to a Button hyperlinked to the youtube video.
• 2 Changes are implemented exactly as shown in screenshots in Issue #894

Resolves #894

Checklist before requesting a review

• [x] I have performed a self-review of my code
• [x] I assure there is no similar/duplicate pull request regarding same issue