Prose provides a beautifully simple content authoring environment for CMS-free websites. It's a web-based interface for managing content on GitHub. Use it to create, edit, and delete files, and save your changes directly to GitHub. Host your website on GitHub Pages for free, or set up your own GitHub webhook server.
Prose has advanced support for Jekyll sites and markdown content. Prose detects markdown posts in Jekyll sites and provides syntax highlighting, a formatting toolbar, and draft previews in the site's full layout.
Developers can configure Jekyll sites to take advantage of these and many more features that customize the content editing experience.
Find more headless content management systems.