Ability to exclude certain headings from TOC

[kilimnik]

I am looking for a way to exclude certain headings from the TOC.

For example I want a TOC for this md:

# Header 1

# Header 2 {no_toc}

# Header 3

I would like the resulting TOC to only include the first and third header.
I am unsure if an attribute is the best way to go, as I don't know if it is even possible for the plugin to remove it from the markdown. So it wouldn't get rendered.

Another idea would be to add a list or a callback as an option. The list would contain the headings to ignore. The callback would be called on each heading and the result would decide if this heading should be ignored.

I am also a little bit unsure about subheadings:

# Header 1

## Subheader 1.1

## Subheader 1.2

# Header 2 {no_toc}

## Subheader 2.1

## Subheader 2.2

# Header 3

I think if the second header should be excluded all it's subheadings should be excluded too.

I already saw, there was a similar Issue #15. But that got closed without a real resolution.

I am open to contributing and adding the feature myself.