demo script updates (#934)

Demo script updates.  Record-replay, a bugfix in the canary demo script, etc.

demos/cncf-webinar/hello.js

@@ -0,0 +1,7 @@
+
+module.exports = async function(context) {
+    return {
+        status: 200,
+        body: "Hello, world!\n"
+    };
+}