message: Listen to the scroll events on the scroll container.
  This makes the scroll wheel also work on the gaps between viewer elements.
diff: @@ -146,7 +146,9 @@ export class TerminalCanvas extends ThemeableElementBase implements AcceptsConfi
  this._virtualScrollArea.scrollTo(this._scrollBar.getPosition());
  });
  - this._scrollArea.addEventListener('wheel', this._handleMouseWheel.bind(this), true);
  + this._scrollContainer.addEventListener('wheel', (ev: WheelEvent): void => {
  + this._handleMouseWheel(ev);
  + }, true);
  this._scrollArea.addEventListener(EVENT_RESIZE, this._handleVirtualScrollableResize.bind(this));
  this._scrollArea.addEventListener(TerminalViewer.EVENT_KEYBOARD_ACTIVITY, () => {
  