Add screenReaderMode to typings

typings/xterm.d.ts

@@ -72,6 +72,13 @@ declare module 'xterm' {
      */
     rows?: number;
 
+    /**
+     * Whether screen reader support is enabled. When on this will expose
+     * supporting elements in the DOM to support NVDA on Windows and VoiceOver
+     * on macOS.
+     */
+    screenReaderMode?: boolean;
+
     /**
      * The amount of scrollback in the terminal. Scrollback is the amount of rows
      * that are retained when lines are scrolled beyond the initial viewport.