Ask HN: Transform a static landing page into a CMS?

Hi,

I'm a web freelancer who plans to build some landing pages for my clients (to promote their products and capture emails).

I'll build the landing page myself with some HTML/CSS/JS. But then I'd like to give my clients some kind of backoffice so they can edit the content of the page itself if needed.

How can I easily "convert" my static landing pages into a really simple CMS for my clients? I'm looking for something lightweight.

Like adding some info in my html tags, then running some scripts, and I automatically get some kind of backoffice to edit the page, with no database needed.

Thanks!