Added docker file and some explanation

Dockerfile

@@ -0,0 +1,10 @@
+FROM debian:buster-slim
+MAINTAINER Salvador E. Tropea <set@ieee.org>
+LABEL Description="Minimal KiCad image based on Debian"
+
+RUN echo "deb http://deb.debian.org/debian buster-backports main" >> /etc/apt/sources.list && \
+	apt-get -y update && \
+	apt-get -y install -t buster-backports --no-install-recommends kicad kicad-libraries && \
+	apt-get -y autoremove && \
+	rm -rf /var/lib/apt/lists/*
+

README.md

@@ -1,2 +1,31 @@
 # kicad_debian
-Docker image for KiCad on Debian GNU/Linux
+
+Docker image for KiCad on Debian GNU/Linux.
+
+The main objetive is to use it as a base for KiCad automation in CI/CD environments.
+
+The images are uploaded to [Docker Hub](https://hub.docker.com/repository/docker/setsoft/kicad_debian).
+
+The current tags are:
+
+* **10.3-5.0.2** is Debian 10.3 + KiCad 5.0.2 (default stable)
+* **10.3-5.1.5** (same as **latest**) is Debian 10.3 + KiCad 5.1.5 (backport)
+
+The installations are minimal, but contains schematic and footprint libraries.
+The 3D models aren't included, they weight 10 times the size of these images.
+
+If you want to run interactively use:
+
+```
+export USER_ID=$(id -u)
+export GROUP_ID=$(id -g)
+docker run -it -v /tmp/.X11-unix:/tmp/.X11-unix -e DISPLAY=$DISPLAY \
+    --user $USER_ID:$GROUP_ID \
+    --env NO_AT_BRIDGE=1 \
+    --workdir="/home/$USER" \
+    --volume="/etc/group:/etc/group:ro" \
+    --volume="/home/$USER:/home/$USER:rw" \
+    --volume="/etc/passwd:/etc/passwd:ro" \
+    --volume="/etc/shadow:/etc/shadow:ro" \
+    --volume="/home/$USER:/home/$USER:rw" \
+    setsoft/kicad_auto:10.3-5.1.5 kicad