Updating Compose documentation

- Split out commands into individual pages for maintainability
- Add full usage in commands pages for usability
- Updated description of the run command
- adding in Aanand's comment

Signed-off-by: Mary Anthony <mary@docker.com>

docs/reference/port.md

@@ -0,0 +1,22 @@
+<!--[metadata]>
++++
+title = "port"
+description = "Prints the public port for a port binding.s"
+keywords = ["fig, composition, compose, docker, orchestration, cli,  port"]
+[menu.main]
+parent = "smn_compose_cli"
++++
+<![end-metadata]-->
+
+# port
+
+```
+Usage: port [options] SERVICE PRIVATE_PORT
+
+Options:
+--protocol=proto  tcp or udp [default: tcp]
+--index=index     index of the container if there are multiple
+                  instances of a service [default: 1]
+```
+
+Prints the public port for a port binding.