Provide documentation in tools

[dgriffon]

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As a Jahia Administrator

I want to Get information about what tools is meant for and the possible options

In order to Know what I can do with the tools

Notes

A markdown file that matches the name of the tool (jsp or menu entry) can be provided.
If found, the documentation of the tool can be displayed either as a modal or at the bottom of the tool itself.
This allows to provide documentation to any external tools.
We can display the documentation in the footer or with a link that opens a modal in the tools index.
This requires a markdown interpreter to display the documentation properly

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• Before closing this issue, ensure it follows our Definition of Done

[romain-pm]

I don't think that we'll be able to prioritize this for now, but that's definitely a good idea.
@GauBen FYI