Add lean multi-stage Dockerfile and GitHub Actions workflow

[ricardoalcantara]

I'd like to contribute with Docker support to this project. My company has a policy that restricts employees from pasting documents on external websites, so being able to self-host the tool via a Docker image makes it much more accessible in those environments — no network dependency, no data leaving the machine.

What's included

• Dockerfile — multi-stage build to keep the final image lean (~25–40 MB):

  1. Build (node:20-alpine) — installs dependencies and runs vite build
  2. Serve (nginx:alpine) — copies only the dist/ folder with a minimal SPA-friendly nginx config

• .github/workflows/docker.yml — builds and pushes the image to GHCR on every push to main

Usage

docker build -t markdown-live-preview .
docker run -p 8080:80 markdown-live-preview

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Feel free to close this if it doesn't fit the project's goals.