doc: add a note about running virtme-ng inside docker

Add an example on how to use virtme-ng inside a docker container with an
ubuntu-22.04 image.

Moreover, add a note to the troubleshooting section, mentioning about
the udev requirement to properly support stdin/stdout/stderr
redirection with virtme-ng instances running inside docker.

This fixes issue #51.

Signed-off-by: Andrea Righi <[email protected]>

README.md

@@ -281,6 +281,23 @@ Examples
    (virtme-ng is started in graphical mode)
 ```
 
+ - Run virtme-ng inside a docker container (using virtme-ng directly from the
+   source repository):
+```
+   $ docker run -it ubuntu:22.04 /bin/bash
+   # apt update
+   # echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections
+   # apt install --yes git qemu-kvm udev iproute2 busybox-static \
+     coreutils python3-requests libvirt-clients kbd kmod file rsync zstd udev
+   # cd ~
+   # git clone --recursive https://github.com/arighi/virtme-ng.git
+   # apt download linux-image-unsigned-6.5.0-14-generic # replace this with any other kernel
+   # apt download linux-modules-6.5.0-14-generic # replace this with any other kernel
+   # for f in *.deb; do dpkg -x $f .; done
+   # ./virtme-ng/vng -r boot/vmlinuz-6.5.0-14-generic -- uname -r
+   6.5.0-14-generic
+```
+
 Implementation details
 ======================
 
@@ -343,6 +360,14 @@ command when running make.
 Troubleshooting
 ===============
 
+ - Running virtme-ng instances inside docker: in case of failures/issues,
+   especially with stdin/stdout/stderr redirections, make sure that you have
+   `udev` installed in your docker image and run the following command before
+   using `vng`:
+```
+  $ udevadm trigger --subsystem-match --action=change
+```
+
  - If you get permission denied when starting qemu, make sure that your
    username is assigned to the group `kvm` or `libvirt`:
 ```