Add WindowOptions to docs

Typedoc doesn't currently support @ignore - it uses @hidden. (See
TypeStrong/typedoc#198). Adding @hidden
alongside the @ignore correctly supresses the fin.WindowOptions, which
was generating invalid json (an array within an array for the child
property), and correctly creates the WindowOptions documentation.

Author: JDawes-ScottLogic

packages/api-specification/interface/openfin-extension.ts

@@ -1,5 +1,6 @@
 /**
  * @ignore
+ * @hidden
  */
 declare namespace fin {
   interface OpenFinWindow {

packages/api-specification/interface/window-extension.ts

@@ -7,13 +7,15 @@
 
 /**
  * @ignore
+ * @hidden
  */
 declare interface Screen {
   orientation: Orientation;
 }
 
 /**
  * @ignore
+ * @hidden
  */
 interface Orientation {
   angle: number;