Lint to detect dangling identifiers in docs (#240).

lib/src/rules.dart

Index: lib/src/rules.dart
diff --git a/lib/src/rules.dart b/lib/src/rules.dart
index 44cef7012db98d1e041229693b8d0ce4cf8e76cc..9ba7acf8b295bb5665bba7986b1f589a7d6e2b6d 100644
--- a/lib/src/rules.dart
+++ b/lib/src/rules.dart
@@ -17,6 +17,7 @@ import 'package:linter/src/rules/avoid_init_to_null.dart';
 import 'package:linter/src/rules/avoid_return_types_on_setters.dart';
 import 'package:linter/src/rules/await_only_futures.dart';
 import 'package:linter/src/rules/camel_case_types.dart';
+import 'package:linter/src/rules/comment_references.dart';
 import 'package:linter/src/rules/constant_identifier_names.dart';
 import 'package:linter/src/rules/control_flow_in_finally.dart';
 import 'package:linter/src/rules/empty_constructor_bodies.dart';
@@ -54,6 +55,7 @@ final Registry ruleRegistry = new Registry()
   ..register(new AvoidInitToNull())
   ..register(new AwaitOnlyFutures())
   ..register(new CamelCaseTypes())
+  ..register(new CommentReferences())
   ..register(new ConstantIdentifierNames())
   ..register(new UnrelatedTypeEqualityChecks())
   ..register(new EmptyConstructorBodies())