Describe how to use Docker for the consoledemo

Docker.md

+Docker for running a consoledemo
+================================
+
+Dockerfile
+----------
+
+The file Docker container is built in two stages:
+1. Setup a build environment, containing all essential build packages. It
+   clones the "dijkema" git tree and uses the default branch ("jeroen").
+2. Setup the execution environment. The artefacts from the build environment
+   are copied in here, a non-root user is created, and the demo is started.
+
+Creating a Docker image
+-----------------------
+
+To run the image locally on your pc, build the docker image named
+'consoledemo':
+```shell
+docker build --tag consoledemo .
+```
+
+Then run it:
+```shell
+docker run -it -p 8000:8000 consoledemo
+```
+
+Uploading to the container registry
+-----------------------------------
+
+It's also possible to upload the container image to the container registry, so
+that it can be used by others.
+
+Instead of creating a tag "consoledemo", create a tag like
+`gitlabregistry.camras.nl:5050/<user>/dt_ctrl:<version>`, for example
+`gitlabregistry.camras.nl:5050/michel/dt_ctrl:20210427` With `docker login
+gitlabregistry.camras.nl:5050` you can login to the registry (please pay
+attention to the warnings on storing your credentials), and then push the
+image: `docker push gitlabregistry.camras.nl:5050/<user>/dt_ctrl:<version>`.
+
+Todo
+----
+
+Build the container from a gitlab ci-cd pipeline. So instead of executing the
+git-pull in the docker file, prepare a container image to be used by the
+gitlab ci-cd, and the gitlab runner will then populate the source tree in the
+build environment. Ideally this pipeline will then create a tar file or .deb
+Debian package for installing on the console and controller, and also a
+docker image for a consoledemo.