And by that I mean,
An http server that serves word-like rich formatted text documents and includes a web-based rich formatting text editor to write and edit these documents.
With some searching I found these might be candidates
Ghost
WriteFreely / Write.as
Plume
And maybe the following editors in some kind of standalone mode
TipTap
Editor.js
Quill.js
CKEditor 5
Slate.js
Grav is nice, as it creates flat files for the front end, instead of server side/database driven pages. That makes it super fast to load.