[FIX] Adding Types for the new scoped classNames feature (#143)

types/index.d.ts

@@ -713,6 +713,11 @@ declare module 'driver.js' {
        * @default auto
        */
       position?: string;
+
+      /**
+       * className for the popover on element
+       */
+      className?: string;
     }
 
     interface DriverOptions {
@@ -795,6 +800,11 @@ declare module 'driver.js' {
        */
       prevBtnText?: string;
 
+      /**
+       * className for the driver popovers
+       */
+      className?: string;
+
       /**
        * Callback to be called when element is about to be highlighted
        * @param {Driver.Element} element