fix: unexpected console error from pendo messsages in demo

The embed javascript demo was rendering an unexpected error
message in the javascript console. The type of message data
is now checked prior to parsing it.

demo/message_utils.ts

@@ -406,7 +406,7 @@ class EmbedFrameImpl implements EmbedFrame {
         if (data) {
           let parsedData: any
           try {
-            parsedData = JSON.parse(data)
+            parsedData = typeof data === 'object' ? data : JSON.parse(data)
           } catch (error) {
             console.error('data is not json', { data })
           }