Add dockerfile and gitlab CI instructions

.gitlab-ci.yml

+image: git.embl.de:4567/grp-bio-it-workshops/intermediate-python
+
+variables:
+  LC_ALL: "C.UTF-8"
+  MAKEFLAGS: "-j 8"
+
+pages:
+  stage: deploy
+  script:
+    - make lesson-check
+    - make lesson-check-all
+    - make site
+    - mv _site public
+  artifacts:
+    paths:
+      - public
+  only:
+    - master

Dockerfile

+FROM jekyll/jekyll
+
+RUN apk --no-cache add \
+    py3-yaml \
+ && gem install json kramdown

build-push-docker.sh

+#!/usr/bin/env bash
+
+set -euxo pipefail
+
+docker build -t git.embl.de:4567/grp-bio-it-workshops/intermediate-python .
+
+# If successful update the image
+docker login git.embl.de:4567
+docker push git.embl.de:4567/grp-bio-it-workshops/intermediate-python