Expand beian options for users in mainland China

[InterHorse]

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?

No feature of the public security record.

Issue resolved: N/A

What is the new behavior?

For Chinese users, except for the ICP record, they need public security record, too. I added this feature in this pull request.

• Screenshots with this changes:
  

• Link to demo site with this changes: https://www.matalking.com/

How to use?

In NexT _config.yml:

footer:
  beian:
    enable: true
    icp: 京ICP备19031359号-2
    gongan_id: 11010502038639
    gongan_num: 京公网安备 11010502038639号
    gongan_icon_url: /uploads/beian.png

Does this PR introduce a breaking change?

• Yes.
• No.

[welcome]

Thanks so much for opening your first PR here!

[CLAassistant]

All committers have signed the CLA.

[1v9]

原有的备案选项扩充即可，不用新增选项。

[InterHorse]

原有的备案选项扩充即可，不用新增选项。

It has been modified.

[stevenjoezhang]

需要在这里更新一下文档：https://github.com/theme-next/theme-next.org/pulls

GitHub

theme-next/theme-next.org

The website for NexT theme. Contribute to theme-next/theme-next.org development by creating an account on GitHub.

[InterHorse]

需要在这里更新一下文档：https://github.com/theme-next/theme-next.org/pulls

GitHub**theme-next/theme-next.org**The website for NexT theme. Contribute to theme-next/theme-next.org development by creating an account on GitHub.

请问文档需要改什么地方？

GitHub

theme-next/theme-next.org

The website for NexT theme. Contribute to theme-next/theme-next.org development by creating an account on GitHub.

[InterHorse]

需要在这里更新一下文档：https://github.com/theme-next/theme-next.org/pulls

GitHub**theme-next/theme-next.org**The website for NexT theme. Contribute to theme-next/theme-next.org development by creating an account on GitHub.

目前文档中好像没有关于大陆用户备案的使用说明。
https://theme-next.org/docs/theme-settings/footer
应该在这个文档里，但是目前没有。 @stevenjoezhang

[1v9]

你可以补上

[1v9]

照着 Site Copyright Name 简单陈述即可。

[InterHorse]

照着 Site Copyright Name 简单陈述即可。

@1v9 已补

[welcome]

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

[1v9]

@all-contributors please add @MartinMa94 for code, doc

[allcontributors]

@1v9

I've put up a pull request to add @MartinMa94! 🎉