Add load json prompt example (#1776)

Hi, I just want to add a PR on the prompt serialization examples of
loading from JSON so that it can contain the same as loading from YAML.

docs/modules/prompts/examples/prompt_serialization.ipynb

@@ -120,6 +120,25 @@
     "!cat simple_prompt.json"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "de75e959",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "prompt = load_prompt(\"simple_prompt.json\")\n",
+    "print(prompt.format(adjective=\"funny\", content=\"chickens\"))"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "d1d788f9",
+   "metadata": {},
+   "source": [
+    "Tell me a funny joke about chickens."
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "d788a83c",