Update CDN URL

[799953468]

PR Checklist

• The commit message follows guidelines for NexT.
• 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

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

What is the current behavior?

Issue resolved:

What is the new behavior?

• Link to demo site with this changes:
• Screenshots with this changes:

How to use?

updated the comment

[welcome]

Thanks so much for opening your first PR here!

[CLAassistant]

All committers have signed the CLA.

[stevenjoezhang]

There is no need to update the CDN version of animate_css. See the description in #41
Thanks!

[stevenjoezhang]

Internal version means the version in source/lib: https://github.com/next-theme/hexo-theme-next/tree/master/source/lib
These files are not changed so it's not necessary to update the version.

See also #72

[stevenjoezhang]

This link returns 404:

curl -I https://cdnjs.cloudflare.com/ajax/libs/mathjax/3.0.6/es5/tex-mml-chtml.js
HTTP/2 404 
date: Sun, 26 Jul 2020 02:31:50 GMT
content-type: text/html; charset=utf-8
served-in-seconds: 0.001
cf-cache-status: HIT
age: 35
expires: Sun, 26 Jul 2020 06:31:50 GMT
cache-control: public, max-age=14400
cf-request-id: 042a8f67c7000092ec5dbfc200000001
expect-ct: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
strict-transport-security: max-age=15780000; includeSubDomains
server: cloudflare
cf-ray: 5b8ab4ec7d8f92ec-SJC
alt-svc: h3-27=":443"; ma=86400, h3-28=":443"; ma=86400, h3-29=":443"; ma=86400

The next release of MathJax would be 3.1.0 and including breaking changes. I will open another PR to fix it.

[799953468]

@stevenjoezhang Sorry, it's my problem.

[stevenjoezhang]

@799953468 That's all right. Thanks for your contribution!
There is no description about CDN in CONTRIBUTING.md, I will update it later.

[welcome]

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