Add proxy to examples.json

examples.json

@@ -257,6 +257,14 @@
         "name": "page-to-extension-messaging",
         "description": "Demonstrates how a web page and a content script can exchange messages. Visit https://mdn.github.io/webextensions-examples/content-script-page-script-messaging.html for the demo."
     },
+    {
+        "javascript_apis": [
+            "proxy.registerProxyScript",
+            "proxy.onProxyError"
+        ],
+        "name": "proxy-blocker",
+        "description": "Uses the proxy API to block requests to specific hosts."
+    },
     {
         "javascript_apis": [
             "storage.local"