add echo example

examples/echo/README.md

@@ -0,0 +1,31 @@
+# Echo Service example
+
+```
+podman-compose up
+```
+
+Test the service with `curl like this`
+
+```
+$ curl -X POST -d "foobar" http://localhost:8080/; echo
+
+CLIENT VALUES:
+client_address=10.89.31.2
+command=POST
+real path=/
+query=nil
+request_version=1.1
+request_uri=http://localhost:8080/
+
+SERVER VALUES:
+server_version=nginx: 1.10.0 - lua: 10001
+
+HEADERS RECEIVED:
+accept=*/*
+content-length=6
+content-type=application/x-www-form-urlencoded
+host=localhost:8080
+user-agent=curl/7.76.1
+BODY:
+foobar
+```