Update README.md

Install

-------

Just ADD the file [`docker-init.sh`][1] (and optionally

[`docker-entrypoint.sh`][2] to your docker images like so:

Just ADD the file [`docker-init.sh`][1] to your docker images like so:

```

ADD https://code.kodo.org.uk/kodo.org.uk/docker-init/raw/master/docker-init.sh <TARGET-PATH>

```

To use [`docker-entrypoint.sh`][2] `docker-init.sh` must go in `/lib/`:

```

ADD https://code.kodo.org.uk/kodo.org.uk/docker-init/raw/master/docker-init.sh /lib/docker-init.sh

ADD https://code.kodo.org.uk/kodo.org.uk/docker-init/raw/master/docker-entrypoint.sh /bin/entrypoint

ENTRYPOINT ["/bin/entrypoint"]

```

[1]: https://code.kodo.org.uk/kodo.org.uk/docker-init/blob/master/doc/docker-init.md "docker-init.sh documentation"