Add support for kramdown's no_toc

[allejo]

Description

Kramdown's official method of hiding a heading from their auto-TOC is to use the no_toc class. I already have the capability of extracting IDs, so I'm thinking to extract classes and check for no_toc there.

Let's see how performance hungry this feature would be.

Sample Usage

# Contents header
{:.no_toc}

* A markdown unordered list which will be replaced with the ToC, excluding the "Contents header" from above
{:toc}

# H1 header

## H2 header

Expected TOC

- H1 header
  - H2 header

[stale]

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[m5o]

Do you think something similar to this would also possible?

https://github.com/toshimaru/jekyll-toc#skip-toc-section
Headings are ignored inside the element which has no_toc_section class.

Use case: Skip the headings for certain sections e.g. html code examples or callouts
🔗 https://github.com/twbs/bootstrap/pull/27417/files

[allejo]

Do you think something similar to this would also possible?

toshimaru/jekyll-toc#skip-toc-section
Headings are ignored inside the element which has no_toc_section class.

Not in a simple and sane manner; see the discussion in #3. I'd prefer to keep this project as simple and lightweight as possible. But if you can come up with a robust solution, I'm open to exploring it.