feat(toc): Support unnumbered headings

[Cerallin]

What does it do?

This PR adds a new feature to hexo to control the numbering of headings by the data-toc-unnumbered attribute.

Using pandoc, code written in markdown like

### Title { data-toc-unnumbered=true }

will be rendered as

<h3 data-toc-unnumbered="true" id="title">Title</h3>

and finally unnumbered in TOC.

Screenshots

Pull request tasks

• Add test cases for the changes.
• Passed the CI test.

This PR should be merged after hexojs/hexo-util#269 merged and published with hexo-util.

Closes #4860.

[github-actions]

How to test

git clone -b feat/toc-support-unnumbered-headings https://github.com/Cerallin/hexo.git
cd hexo
npm install
npm test

[yoshinorin]

@Cerallin

Now, I'm testing this PR with hexojs/hexo-util#269 in my machine.
My understanding, according to your explanation & hexojs/hexo-util#269 test code the below markdown...

### Title { data-toc-unnumbered=true }

will be reneder belows.

<h3 id="title" data-toc-unnumbered="true">Title</h3>

But, it can't.
Would you please explain how to add an attribute to markdown headings? Or, would you please see the demo source code to me?

Thank you :)

[Cerallin]

@yoshinorin

This is because I am using hexo-renderer-pandoc.
You can also generate an HTML file directly with pandoc:

pandoc test.md -o test.html

Ref: https://pandoc.org/MANUAL.html#extension-header_attributes

[yoshinorin]

Waiting for the release of hexo-util 2.6.0

[yoshinorin]

@Cerallin
Sorry so late reply.
We merged hexo-util 2.6.0. Would you please rebase?

Thank you :)

[Cerallin]

Cherry-picked my commit. :)

[yoshinorin]

LGTM.
Thank you :)