follow up for #25578, add `@checked` to package:meta

pkg/meta/CHANGELOG.md

+## 1.0.3
+* Introduce `@checked` to override a method and tighten a parameter
+    type (SDK issue [25578](https://github.com/dart-lang/sdk/issues/25578)).
+
+    ```dart
+    import 'package:meta/meta.dart' show checked;
+    class View {
+      addChild(View v) {}
+    }
+    class MyView extends View {
+      // this override is legal, it will check at runtime if we actually
+      // got a MyView.
+      addChild(@checked MyView v) {}
+    }
+    main() {
+      dynamic mv = new MyView();
+      mv.addChild(new View()); // runtime error
+    }
+    ```
+
 ## 1.0.2
 * Introduce `@visibleForTesting` annotation for declarations that may be referenced only in the library or in a test.
 
 ## 1.0.1
 * Updated `@factory` to allow statics and methods returning `null`.
 
 ## 1.0.0
 * First stable API release.
 
 ## 0.12.2
@@ skipping 15 matching lines @@
 constructor must use the keyword `const` unless one or more of the
 arguments to the constructor is not a compile-time constant.
 
 ## 0.9.0
 * Introduce `@protected` annotation for members that must only be called from
 instance members of subclasses.
 * Introduce `@required` annotation for optional parameters that should be treated
 as required.
 * Introduce `@mustCallSuper` annotation for methods that must be invoked by all
 overriding methods.