A simple Docker container compiling Nginx from source together with Openssl from the the latest code on Github and the branch supporting TLS 1.3 draft 18.
Size of built image: 225 MB
This project is under WTFPL. So you can pretty much do whatever you want with it.
Do be warned this has had not been tested for production, and the Dockerfile is written by a person with very little knowledge about all this stuff.