Update Obtain credentials using TokenLibrary.ipynb

Author: nirav2

Notebooks/Spark.NET C#/Obtain credentials using TokenLibrary.ipynb

@@ -8,6 +8,16 @@
   "nbformat": 4,
   "nbformat_minor": 2,
   "cells": [
+    {
+      "cell_type": "code",
+      "execution_count": null,
+      "outputs": [],
+      "metadata": {},
+      "source": [
+        "For latest documentation please run TokenLibrary.help() from Notebook\n"
+      ],
+      "attachments": {}
+    },
     {
       "cell_type": "code",
       "execution_count": null,