Add integrity SHA-256 to externally loaded asset (#40)

Even though this POC is neither actively used nor maintained, this satisfies CodeQL and ensures the right resource is always loaded from the external URL.

pocs/distributed_collab/priv/static/index.html

@@ -24,7 +24,7 @@
     <h1>Collaborative JSON editing</h1>
     <div id="container"></div>
 
-    <script src="https://cdnjs.cloudflare.com/ajax/libs/fast-json-patch/3.1.1/fast-json-patch.js"></script>
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/fast-json-patch/3.1.1/fast-json-patch.js" integrity="sha256-Qf9lvjtL7xCt5niiMAxwQDC+TowsJAqGo7aA4TEYQRw=" crossorigin="anonymous"></script>
 
     <script>
       const container = document.querySelector("#container");