feat: Improve the blog sidebar by adding a highlighter to active section

[chauhan-varun]

What kind of change does this PR introduce?

Enhancement: I've implemented highlighting for the sidebar navigation in the blog section.

Issue Number:

• Closes ✨ Enhancement: Improve the blog sidebar by adding a highlighter to active section #1508

Screencast.from.2025-06-14.23-02-49.webm

Screencast.from.2025-06-14.23-27-51.webm

If relevant, did you update the documentation?
NA

Summary
The implementation works by:

• Observing all heading elements (h1, h2, h3, h4) on the page
• When a heading enters the viewport (with appropriate margins to make it feel natural), it sets that heading's ID as the active section
• The sidebar links check if their target section matches the active section ID and apply appropriate styling

Now when you scroll through a blog post, the sidebar will automatically highlight the section you're currently reading, making it easier to keep track of your position in the document. This works in both light and dark modes with appropriate color schemes for each.

Does this PR introduce a breaking change?
NA

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

[github-actions]

Hi @chauhan-varun! Thanks a lot for your contribution!

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Thanks a lot!