feat(ci): dockerized runner deployment for course

[tomasvh]

This PR introduces the following:

• New Lab 3 instructions on how to get up a self hosted runner in Docker setting instead of installed version using GitHubs own documentation.
• Introduces well documented Dockerfile on what is installed on said image.
• Introduces well documented docker-compose.yml which deploys and injects variables.
• Introduces well documented start.sh that gets copied in and run in the docker container, explains what is going on in comments.
• Introduces an ignore on .env file.
• Introduces a envTemplate file which is to be used by students.
• Updates README.md with lab instructions in regards to setting up a personal access token, dealing with the .env file, fixing potential line ending problems and sourcing it for the docker compose files to use
• Introduces a Docker deployment of a GitHub runner in arm64 and/or x64 architecture

The instructions on how to set it up is designed to give understanding on what is going on in the separate files

The instructions and deployment is run and tested on a Windows 11 laptop(amd64 architecture) and a Mac (arm64).