Add tutorial for avro dataset API (tensorflow#1250)

Author: burgerkingeater

docs/tutorials/avro.ipynb

@@ -138,7 +138,16 @@
       "metadata": {
         "id": "dX74RKfZ_TdF"
       },
-      "outputs": [],
+      "outputs": [
+        {
+          "name": "stdout",
+          "output_type": "stream",
+          "text": [
+            "tensorflow-io version: 0.17.0\n",
+            "tensorflow version: 2.4.0\n"
+          ]
+        }
+      ],
       "source": [
         "print(\"tensorflow-io version: {}\".format(tfio.__version__))\n",
         "print(\"tensorflow version: {}\".format(tf.__version__))"