WebDocGen is a tool intended for generating web documentation/user manuals for websites. Developers can describe their documentation in Markdown, interspersing it with Javascript codeblocks that will be executed in a browser, and whose “results” will be interpolated into an output Markdown file. This idea is inspired by the Literate Programming paradigm, and specifically Emacs’s Org Mode.
The beauty of Markdown as an input/output format is that it can be converted to practically any other format. Coupled with a Pandoc template, you can trivially convert it to HTML or into a PDF with hardly any setup. Also, static site generators like Hugo and Jekyll have tons of open source themes that you can use, and allow you to take Markdown files and turn them into full-fledged documentation websites.
This example looks at Google.com, and goes through the main features of WebDocGen. Unfortunately, it does not render properly within the README as a Markdown source block, since the nested code blocks confuse the parser.
You can see this example compiled to HTML using the linked Pandoc templates here. To view the (brief) source for the compilation: see here.