Merge pull request #1782 from astefanutti/pr-wheel

Use WheelEvent.deltaY instead of WheelEvent.wheelDeltaY for wheel event

src/Terminal.ts

@@ -985,7 +985,7 @@ export class Terminal extends EventEmitter implements ITerminal, IDisposable, II
           : 65;
           break;
         case 'wheel':
-          button = (<WheelEvent>ev).wheelDeltaY > 0
+          button = (<WheelEvent>ev).deltaY < 0
             ? 64
           : 65;
           break;