Adding missing title in builder.md
addresses
---
+title: Dockerfile reference
description: "Dockerfiles use a simple DSL which allows you to automate the steps you would normally manually take to create an image."
keywords: "builder, docker, Dockerfile, automation, image creation"
redirect_from:
@@ -14,7 +15,6 @@ redirect_from:
will be rejected.
-->
-# Dockerfile reference
Docker can build images automatically by reading the instructions from a
`Dockerfile`. A `Dockerfile` is a text document that contains all the commands a
