IntersectionObserver about TOC

[jiangtj]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines.
• Tests for the changes was maked (for bug fixes / features).
  • Muse | Mist have been tested.
  • Pisces | Gemini have been tested.
• Docs in NexT website have been added / updated (for features).

PR Type

What kind of change does this PR introduce?

• Bugfix.
• Feature.
• Code style update (formatting, local variables).
• Refactoring (no functional changes, no api changes).
• Build related changes.
• CI related changes.
• Documentation content changes.
• Other... Please describe:

What is the current behavior?

Issue resolved: N/A

What is the new behavior?

• Screenshots with this changes: N/A
• Link to demo site with this changes: N/A

How to use?

In NexT _config.yml:

...

Does this PR introduce a breaking change?

• Yes.
• No.

[jiangtj]

Return to the previous title when you slide up
old

new

When refreshing, navigate to the current title
old

new

[jiangtj]

master branch: https://jiangtj.gitlab.io/next-test/master/post/many-title/
fix-observer-index branch: https://jiangtj.gitlab.io/next-test/gemini/post/many-title/

Hexo

Many Title

title0csabrtytnmmsdgvtryhntryjnuy csabrtytnmmsdgvtryhntryjnuy ceabrys,nfrlehgtrlhyt vebytityum,uftmjuy csabrtytnmmsdgvtryhntryjnuy ceabrys,nfrlehgtrlhyt vebytityum,uftmjuy csabrtytnmmsdgvtryhntryjnuy

Hexo

Many Title

title0csabrtytnmmsdgvtryhntryjnuy csabrtytnmmsdgvtryhntryjnuy ceabrys,nfrlehgtrlhyt vebytityum,uftmjuy csabrtytnmmsdgvtryhntryjnuy ceabrys,nfrlehgtrlhyt vebytityum,uftmjuy csabrtytnmmsdgvtryhntryjnuy

[jiangtj]

还发现个问题，非常快滑动的时候，未观察到
I found another issue, when I slide very quickly, didn’t observe it.