link ctor -> builder

README.md

@@ -55,7 +55,10 @@ language.
 
 ## Contributing
 
+Contributions are very welcome!
+
 You should start with [the template](template.md). Copy it into the appropriate
 directory, edit it, and submit a PR. You might not want every section, and you
-might want to add extra sections. Correction and elaboration PRs are also very
-welcome.
+might want to add extra sections.
+
+Correction and elaboration PRs are very welcome.

idioms/ctor.md

@@ -33,5 +33,5 @@ impl<T> Vec<T> {
 
 ## See also
 
-The builder pattern for constructing objects where there are multiple
+The [builder pattern](../patterns/builder.md) for constructing objects where there are multiple
 configurations.