Update for compatibility with Dart version 3

.github/workflows/dart.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        sdk: [stable, 2.18.2]
+        sdk: [stable, 3.0.0]
 
     steps:
       - uses: actions/checkout@v2

CHANGELOG.md

@@ -8,6 +8,12 @@ announcements on the StageXL forum or use one of the support links below:
   * StageXL GitHub <https://github.com/bp74/StageXL/issues>
   * StageXL StackOverflow: <http://stackoverflow.com/questions/ask?tags=stagexl>
 
+### 2.2.0
+* Support the latest version of `package:xml`.
+* Update Dart SDK restraint to  ^3.0.0
+* Add drag-drop support to interactive objects. (Pull #360)
+* Add drag-drop support to stage. (Pull #359)
+
 ### 2.1.2
  * Support the latest version of `package:xml`.
  * Update Dart SDK restraint to >= 2.18.0

lib/src/events/event_stream_subscription.dart

@@ -10,7 +10,7 @@ typedef EventListener<T extends Event> = void Function(T event);
 /// used to handle the events. The subscription can also be used to unsubscribe
 /// from the events, or to temporarily pause the events from the stream.
 
-class EventStreamSubscription<T extends Event> extends StreamSubscription<T> {
+class EventStreamSubscription<T extends Event> implements StreamSubscription<T> {
   final int _priority;
   int _pauseCount = 0;
   bool _canceled = false;

pubspec.yaml

@@ -1,16 +1,16 @@
 name: stagexl
-version: 2.1.2
+version: 2.2.0
 description: A fast and universal 2D rendering engine for HTML5 and Dart.
 homepage: http://www.stagexl.org
 repository: https://github.com/bp74/StageXL
 
 environment:
-  sdk: '>=2.18.0 <3.0.0'
+  sdk: '^3.0.0'
 
 documentation: http://www.stagexl.org/docs/api/index.html
 
 dependencies:
-  xml: '>=5.0.0 <7.0.0'
+  xml: '>=6.3.0 <7.0.0'
 
 dev_dependencies:
   build_runner: any