readme, document forward

Author: portertech

README.md

@@ -67,6 +67,23 @@ installed. There are several different behaviors available:
 
 The default value is `true`.
 
+### <a name="config-forward"></a> forward
+
+Suite container port(s) to forward to the host machine. You cannot
+specify the host port in the mappings, Docker does this for you.
+
+Examples:
+
+```
+forward: 8080
+```
+
+```
+forward:
+- 22
+- 80
+```
+
 ## <a name="development"></a> Development
 
 * Source hosted at [GitHub][repo]