Added Dockerfile for containerisation

Dockerfile

+# Dockerfile has three Arguments: base, tag, branch
+# base - base image (default: debian)
+# tag - tag for base mage (default: stable-slim)
+# branch - user repository branch to clone (default: master)
+#
+# To build the image:
+# $ docker build -t <dockerhub_user>/<dockerhub_repo> --build-arg arg=value .
+# or using default args:
+# $ docker build -t <dockerhub_user>/<dockerhub_repo> .
+
+# set the base image. default is debian, optional ubuntu
+ARG base=debian
+# set the tag (e.g. latest, stable, stable-slim : for debian)
+ARG tag=stable-slim
+
+# Base image, e.g. debian:stable-slim
+FROM ${base}:${tag}
+
+LABEL maintainer='Borja Esteban'
+
+# What branch to clone (!)
+ARG branch=master
+
+# Which user and group to use 
+ARG user=worker
+ARG group=standard
+
+# Install system updates and tools
+ENV DEBIAN_FRONTEND=noninteractive
+RUN apt-get update && apt-get install -y --no-install-recommends \
+# Install system updates and tools
+        ca-certificates \
+        git && \
+# Clean up & back to dialog front end
+    apt-get autoremove -y && \
+    apt-get clean -y && \
+    rm -rf /var/lib/apt/lists/*
+ENV DEBIAN_FRONTEND=dialog
+
+# Install user app:
+RUN git clone --depth 1 -b ${branch} https://github.com/BorjaEst/cicd.git app && \
+# Clean up
+    rm -rf /root/.cache/pip/* && \
+    rm -rf /tmp/*
+WORKDIR /app
+
+# Set environments
+ENV LANG C.UTF-8
+
+# Ports to expose
+EXPOSE 8443
+EXPOSE 8080
+
+# Change user context and drop root privileges
+RUN groupadd -r ${group} && \
+    useradd --no-log-init -r -g ${group} ${user}
+USER ${user}
+
+# Start default script
+ENTRYPOINT [ "/app/main" ]
+CMD [ "" ]
+