Implement CriticMarkup

[pierreporte]

CriticMarkup is an extension for Markdown whose goal is to allow authors to add comments or suggestions of modification in a similar way of the features present in Microsoft Word or LibreOffice Writer. Not only a syntax extension, CriticMarkup can also have a system similar to pull request: the author can accept or reject the modification proposition (still similar to what is already available in common text processors).

Refer to the user’s guide and to the specifications.