Riley Porter

The [`KeyboardEvent.keyCode`](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/keyCode) property is deprecated in favor of [`KeyboardEvent.code`](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/code), which is supported by all browsers except IE. `dart:html` still provides `keyCode` along with all [the KeyCode values](https://api.dart.dev/stable/2.4.1/dart-html/KeyCode-class.html). We should mark...