Make chapter section scroll to current chapter when scroll into view port when expanded

[PikachuEXE]

Pull Request Type

• [ ] Bugfix
• [x] Feature Implementation
• [ ] Documentation
• [ ] Other

Related issue

Description

Currently the chapter section only scroll to current chapter when expanded With this PR it scroll to current chapter when scrolled into view port (becomes visible) which is useful especially on videos with many chapters Users can still scroll around chapters when chapter section is visible

Screenshots

Start a video

Change current timestamp

Scroll back down

Testing

• Find a video with chapters (plenty in LTT)
• Expand chapter section
• Scroll up (and maybe resize window) until chapter section hidden
• Change current timestamp (far away from current one would be easier for testing)
• Scroll down and ensure current chapter at the new timestamp is scrolled to

Desktop

• OS:
• OS Version:
• FreeTube version:

Additional context