Document Docker+GVisor demo

Author: struanb

README.md

@@ -107,7 +107,28 @@ docker exec ubuntu-docker-runcvm bash -c "docker run --rm --runtime=runcvm alpin
 docker rm -fv ubuntu-docker-runcvm
 ```
 
-Launch [OpenWrt](https://openwrt.org/) with port forward to LuCI web UI on port 10080:
+**Docker+GVisor runtime demo** - Launch Ubuntu running Systemd and Docker with [Sysbox](https://github.com/nestybox/sysbox) runtime; then within it run an Alpine _Sysbox_ container; and, _within that_ install dockerd and run a container from the 'hello-world' image:
+
+```console
+cat <<EOF | docker build --tag=ubuntu-docker-gvisor -
+FROM ubuntu:jammy
+RUN apt update && apt -y install apt-utils kmod wget iproute2 systemd \
+    ca-certificates curl gnupg udev dbus && \
+    curl -fsSL https://get.docker.com | bash
+RUN curl -fsSL https://gvisor.dev/archive.key | gpg --dearmor -o /usr/share/keyrings/gvisor-archive-keyring.gpg
+RUN echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/gvisor-archive-keyring.gpg] https://storage.googleapis.com/gvisor/releases release main" >/etc/apt/sources.list.d/gvisor.list && \
+    apt update && \
+    apt-get install -y runsc
+ENTRYPOINT ["/lib/systemd/systemd"]
+ENV RUNCVM_DISKS='/disks/docker,/var/lib/docker,ext4,1G;/disks/sysbox,/var/lib/sysbox,ext4,1G'
+VOLUME /disks
+EOF
+docker run -d --runtime=runcvm -m 2g --name=ubuntu-docker-sysbox ubuntu-docker-sysbox
+docker exec ubuntu-docker-sysbox bash -c "docker run --rm --runtime=sysbox-runc alpine ash -x -c 'apk add docker; dockerd &>/dev/null & sleep 5; docker run --rm hello-world'"
+docker rm -fv ubuntu-docker-sysbox
+```
+
+**Launch [OpenWrt](https://openwrt.org/)** - with port forward to LuCI web UI on port 10080:
 
 ```console
 docker import --change='ENTRYPOINT ["/sbin/init"]' https://archive.openwrt.org/releases/23.05.2/targets/x86/generic/openwrt-23.05.2-x86-generic-rootfs.tar.gz openwrt-23.05.2 && \