I'm currently migrating my website from Jekyll to AstroJS and the experience has been really positive so far. AstroJS, in particular, offers quite a lot of flexibility for writing content in Markdown format. For example, by supporting JSX components (via the MDX extension) and, for more general purposes, by supporting Remark and Rehype plugins. This post gives a short introduction on how to extend Astro's Markdown processing with Remark and Rehype plugins. You will also find a practical example of how to add Mermaid diagram processing with a Rehype plugin.