feat: Add BrowserWindow.setWindowButtonVisibility()

Fixes #12701 and supersedes #13131.

Ideally we would have added `setTitleBarStyle()`, but that is a
significantly more involved change. For example, consider the case where
we switch from `hidden` to `normal`. We would not only have to show the
traffic light buttons, we would also have to switch the window from a
frameless to a framed window and deal with various other window state.
Lets instead implement a simple solution for #12701.

atom/browser/api/atom_api_top_level_window.h

@@ -173,6 +173,7 @@ class TopLevelWindow : public mate::TrackableObject<TopLevelWindow>,
   void MoveTabToNewWindow();
   void ToggleTabBar();
   void AddTabbedWindow(NativeWindow* window, mate::Arguments* args);
+  void SetWindowButtonVisibility(bool visible, mate::Arguments* args);
   void SetAutoHideMenuBar(bool auto_hide);
   bool IsMenuBarAutoHide();
   void SetMenuBarVisibility(bool visible);