Ignore files from being included in the image

[lindhe]

Package version (if known): latest (currently sha256:2193abc2caec9bc599061d6a5874fd2d7d201f55d1673a545af0a0406690e8a4).

Describe the bug

It seems that there are a lot of unnecessary things included in the demo-inveniordm image. This increases the size of the image unnecessarily. I suggest we add a .dockerignore or .containerignore (depending on what container build system you use) that excludes all unnecessary files from the image.

Steps to Reproduce

$ docker run -it --rm ghcr.io/inveniosoftware/demo-inveniordm/demo-inveniordm:latest /usr/bin/ls -al /opt/invenio/src
app_data  docker                   docker-compose.yml  docker-services.yml  Pipfile       README.rst  templates     wipe_recreate.sh
assets    docker-compose.full.yml  Dockerfile          invenio.cfg          Pipfile.lock  static      translations