I’ve published Elmstatic v0.6 with support for elm-markup in order to extend type safety from page layouts to page content. In addition to getting build-time errors when your layout fails to compile (because it’s in Elm), you’ll now get build-time errors if your content fails to parse (if you use elm-markup).
Currently Elmstatic only checks the syntax, but it’s possible to extend this to check the validity of links or other resources, for example. I might implement something like that in future releases.
Actually, you could implement some content checks yourself because you can do anything you like in terms of rendering the content, but links, for example, require passing in a list of valid endpoints, which Elmstatic doesn’t do at the moment.
My release announcement turned into an elm-markup tutorial.