Fix usablica#108 - fix Firefox bug by focusing on "Next" button, so that hitting Enter moves you to the next step

Author: suzannehamilton

intro.js

@@ -419,6 +419,9 @@
       skipTooltipButton.innerHTML = this._options.skipLabel;
     }
 
+    //Set focus on "next" button, so that hitting Enter always moves you onto the next step
+    nextTooltipButton.focus();
+
     //add target element position style
     targetElement.element.className += ' introjs-showElement';