Long time Emacs user used to reading the documentation of most Emacs packages in Info. I'd like to suggest converting your documentation to Org files and then exporting to appropriate formats (Markdown, Texinfo, PDF, ...). Considering, though, the amount of Markdown documentation you already have, perhaps you could just put together a basic Org file that outlines the package and has links to the full manual on Github. That could then be exported to Markdown as the README for Melpa and Texinfo for the local Emacs manual when you publish.
Long time Emacs user used to reading the documentation of most Emacs packages in Info. I'd like to suggest converting your documentation to Org files and then exporting to appropriate formats (Markdown, Texinfo, PDF, ...). Considering, though, the amount of Markdown documentation you already have, perhaps you could just put together a basic Org file that outlines the package and has links to the full manual on Github. That could then be exported to Markdown as the README for Melpa and Texinfo for the local Emacs manual when you publish.