This is jbt's Markdown Editor packaged up in a nice, small, Alpine Linux Docker container.
Well, you could visit the live editor online, but where's the fun when you could be running it locally?
It is also really small ~12Mb.
The container is available on Docker Hub and can be pulled locally by:
docker pull v4tech/markdown-editor
The Dockerfile is on GitHub.
The container automatically listens on port 80, so you need to map that (or let Docker do it for you).
To start the container:
docker run -p 12345:80 --rm -it v4tech/markdown-editor
Then simply point your browser at: http://<dockerIP>:12345