Support for parsing headers in Doxygen \par commands

[alandefreitas]

This issue is dependent on the PR open in the llvm-project: llvm/llvm-project#91100

It refers to its integration in MrDocs once the PR is merged.

[alandefreitas]

It's also possible to emulate the feature by simply parsing the first line as the title.

[alandefreitas]

We need to review whether this feature is still relevant. Do the templates already render the titles of these paragraphs?