Improve Regex

[JakubAndrysek]

Improve or simplify Regex

[JakubAndrysek]

Add support add tags to headers like in mkdocstrings.

It is also possible to integrate a mkdocstrings identifier into a Markdown header:

## ::: my_package.my_module.MyClass
    options:
      show_source: false

The above is equivalent to:

::: my_package.my_module.MyClass
    options:
      show_source: false
      heading_level: 2