Use READMEs from libraries as reference manual introductions
Declt supports a custom introduction via the :introduction
argument, but passing it this way doesn't allow for a lot of customization:
Ideally, standard READMEs should be put in <pre>
tags, markdown files could be processed a bit more to get prettier html out of it.
A solution might be to pass an empty string to Declt as :introduction
and then write our own, correctly formatted html in the empty introduction spot