Function addTopBarButton

addTopBarButton(
    text: string,
    iconClass: Icon,
    onClick: () => void,
    position?: TopBarButtonPosition,
): null | HTMLDivElement
Adds a button to the top bar of the NationStates interface, detecting the correct theme and position.

The top bar is the horizontal bar at the very top of the page (inside div#banner). Buttons can be anchored to the left or right of the central spacer element.
Parameters
- text: string
  The text label for the button.
- iconClass: Icon
  The CSS class for the button's icon (e.g., "globe", "radar").
- onClick: () => void
  A function to be called when the button is clicked.
- position: TopBarButtonPosition = "right"
  Where to place the button in the top bar: "left" or "right".
Returns null | HTMLDivElement
The created button element (HTMLDivElement) or null if a required container element is not found.
- Defined in gui/topBarButton.ts:16