Include non-dockerized target instructions (#25)

I got there with trial and error, being not very trained with docker. But the proposed function works great.

README.md

@@ -81,8 +81,15 @@ For common cases you may want to create an alias in your `~/.profile` (or `~/.ba
     # For ZSH with Oh-My-Zsh! and 'docker' plugin enabled, you can also enable auto-completion:
     #compdef __docker_containers docker-ngrok
 
-Then to the simple example just do `docker-ngrok web_service_container`.
+Then to run the simple example just do `docker-ngrok web_service_container`.
 
+For non dockerized http targets consider this helper function:
+
+    function expose-ngrok() {
+      docker run --rm --net=host -e NGROK_PORT="$1" wernight/ngrok
+    }
+
+and then visit [localhost:4040](http://localhost:4040) for receiving the links.
 
 
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