Add Dockerfile for easy Docker deployment

[darktohka]

Given that there is no Dockerfile available for this project yet, I thought I would create one.

This greatly simplifies deployment on Linux servers.

The strategy I chose for deployment is the following:

• First, the application is compiled using Vercel's pkg into a self-contained executable.
• Second, the application is copied into a lightweight Alpine container that can run the self-contained executable.

Note: The configuration file is mounted as a volume into the Docker container.

The resulting Docker image size is 64.2 MB on arm64.

Information regarding the Dockerfile has been added to the README.