Update config.md
The first line of the file was confusing because it referred to Starlark before defining what Starlark was.  I moved the definition to the first line.
Closes
@@ -7,10 +7,9 @@ category: extending
# Configurations
-This page covers the benefits and basic usage of Starlark configurations. It
-includes how to define build settings and provides examples.
-
-Starlark configuration is Bazel's API for customizing how your project builds.
+This page covers the benefits and basic usage of Starlark configurations,
+Bazel's API for customizing how your project builds. It includes how to define
+build settings and provides examples.
This makes it possible to:
