Update ZMQ Message Reference

ZMQ-Message-Reference.md

@@ -78,6 +78,14 @@ Reply Messages:
 
 ## 'scanRequest'
 
+Data is a JSON scan request. For example:
+```
+    msg = ['estimatedTime',   Scan_Request ]
+```
+
+Reply Messages:
+- `["status","ok"]`
+
 ## 'abortScan'
 
 ## 'pauseScan'