* Update Dockerfile to work with Next.js
- Update to Node 18
- Do not run as root, this also works better with Node
privilege-dropping.
- Update README with new run instructions and adding the
`--rm` flag to avoid leaving a bunch of unused Docker
containers.
- Also change README to recommend building the image locally.
Image builds are pretty fast and the uploaded images get
outdated pretty quickly.
* Add .dockerignore to avoid sending large build contexts
* Typo