Fix keyboard navigation to trigger only if no modifier key is pressed

src/theme/book.js

@@ -33,6 +33,7 @@ $( document ).ready(function() {
     };
 
     $(document).on('keydown', function (e) {
+        if (e.altKey || e.ctrlKey || e.metaKey || e.shiftKey) { return; }
         switch (e.keyCode) {
             case KEY_CODES.NEXT_KEY:
                 e.preventDefault();