Provide and explain docker run examples with and without confinement to localhost

Signed-off-by: Richard Gibson <richard.gibson@gmail.com>

Author: gibson042

README.md

@@ -177,6 +177,14 @@ it is to use the prebuilt image:
 docker run -p 127.0.0.1:80:80 vectorim/element-web
 ```
 
+A server can also be made available to clients outside the local host by omitting the
+explicit local address as described in
+[docker run documentation](https://docs.docker.com/engine/reference/commandline/run/#publish-or-expose-port--p---expose):
+
+```bash
+docker run -p 80:80 vectorim/element-web
+```
+
 To supply your own custom `config.json`, map a volume to `/app/config.json`. For example,
 if your custom config was located at `/etc/element-web/config.json` then your Docker command
 would be: