Adds checking for trailling commas on the project (#670)

* Testing a new linter option for trailling commas

* Checking trailling commas on linter

doc/examples/text/lib/main.dart

@@ -40,10 +40,11 @@ class MyTextBox extends TextBoxComponent {
       height - margin.vertical,
     );
     c.drawRect(
-        innerRect,
-        Paint()
-          ..color = BasicPalette.white.color
-          ..style = PaintingStyle.stroke);
+      innerRect,
+      Paint()
+        ..color = BasicPalette.white.color
+        ..style = PaintingStyle.stroke,
+    );
   }
 }