Adding GUI instructions

Using-the-Blender-GUI-in-containers.md

@@ -0,0 +1,21 @@
+To use the Blender GUI from a container follow this startup script:
+```sh
+XSOCK=/tmp/.X11-unix
+XAUTH=/tmp/.docker.xauth
+touch $XAUTH
+xauth nlist $DISPLAY | sed -e 's/^..../ffff/' | xauth -f $XAUTH nmerge -
+
+docker run \
+        --gpus all \
+        -it \ 
+	-v $XSOCK:$XSOCK:rw \
+	-v $XAUTH:$XAUTH:rw \
+        --device=/dev/dri/card0:/dev/dri/card0 \
+	-e DISPLAY=$DISPLAY \
+	-e XAUTHORITY=$XAUTH \
+        nytimes/blender:2.82-gpu-ubuntu18.04
+```
+
+By launching Blender inside the container with `--device=/dev/dri/card0:/dev/dri/card0` and `--gpus all` you should be able to now use it with both Cycles and Eevee.
+
+> Tested on Ubuntu 19.10 with Docker 19.03.8