Fix utterances/giscus with pjax

[wangjiezhe]

PR Checklist

• The commit message follows guidelines for NexT.
• The changes have been tested (for bug fixes / features).
• Docs in NexT website have been added / updated (for features).

PR Type

• Bugfix.
• Feature.
• Improvement.
• Code style update (formatting, linting).
• Refactoring (no functional changes).
• Documentation.
• Translation.
• Other... Please describe:

What is the current behavior?

Issue resolved:

If we use utterances or giscus comment system with pjax enabled, and use 'og:title' to map blog post with issue or discussion, then the comment does not load correctly if we change to another page. The reason is that utterance/giscus will consult <meta property="og:title" content="***"> in the head, which is not reloaded by pjax. The the comment shown is actually comments for the last page.

What is the new behavior?

The meta tag for 'og:title' is reloaded by pjax, and comments are load correctly.

[welcome]

Thanks so much for opening your first PR here!

[CLAassistant]

All committers have signed the CLA.

[coveralls]

Pull Request Test Coverage Report for Build 8490689155

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 97.416%

---

Totals
Change from base Build 8434159810:	0.0%
Covered Lines:	394
Relevant Lines:	399

---

💛 - Coveralls

[welcome]

Congrats on merging your first pull request here! 🎉 How awesome!