feat: add initial polyglot notebook with C# example

Author: rudironsoni

Threads-and-Tasks.ipynb

@@ -0,0 +1,53 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "id": "db5b302d",
+   "metadata": {
+    "language_info": {
+     "name": "polyglot-notebook"
+    },
+    "polyglot_notebook": {
+     "kernelName": "csharp"
+    }
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Hello, Polyglot Notebook!\n"
+     ]
+    }
+   ],
+   "source": [
+    "Console.WriteLine(\"Hello, Polyglot Notebook!\");"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": ".NET (C#)",
+   "language": "C#",
+   "name": ".net-csharp"
+  },
+  "language_info": {
+   "name": "polyglot-notebook"
+  },
+  "polyglot_notebook": {
+   "kernelInfo": {
+    "defaultKernelName": "csharp",
+    "items": [
+     {
+      "aliases": [],
+      "languageName": "csharp",
+      "name": "csharp"
+     }
+    ]
+   }
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}