[Effen] typo fix: 'cusor' => 'cursor' in editable_text.dart

sky/framework/editing/editable_text.dart

Index: sky/framework/editing/editable_text.dart
diff --git a/sky/framework/editing/editable_text.dart b/sky/framework/editing/editable_text.dart
index 384c1b45f61b6a386b70e4d7f627f6268ff5ef6e..8acff25b04409d1d3ee8379776df9f8452bb0aa7 100644
--- a/sky/framework/editing/editable_text.dart
+++ b/sky/framework/editing/editable_text.dart
@@ -12,7 +12,7 @@ class EditableText extends Component {
     display: inline;'''
   );
 
-  static final Style _cusorStyle = new Style('''
+  static final Style _cursorStyle = new Style('''
     display: inline-flex;
     width: 2px;
     height: 1.2em;
@@ -86,7 +86,7 @@ class EditableText extends Component {
     }
 
     if (_showCursor)
-      children.add(new Container(key: 'cursor', style: _cusorStyle));
+      children.add(new Container(key: 'cursor', style: _cursorStyle));
 
     return new Container(
       style: _style,