fix key listeners to use onKeyDown again (#218)

onKeyPress doesn't appear to work properly on linux chrome

Author: jakemac53

webdev/lib/src/serve/injected/client.dart

@@ -59,7 +59,7 @@ Future<void> main() async {
     }
   });
 
-  window.onKeyPress.listen((e) {
+  window.onKeyDown.listen((e) {
     if (const [
           'd',
           'D',