Updated Notify_Custom_XML (markdown)

Notify_Custom_XML.md

@@ -59,6 +59,40 @@ Send a XML notification to our web server listening on port 80:
 apprise -vv -t "Test Message Title" -b "Test Message Body" \
    xml://xml.server.local
 ```
+
+### Payload Manipulation
+Making use of the `:` on the Apprise URL now allows you to alter and add to the content posted upstream to a remote server.
+
+```bash
+# Add to the payload delivered to the remote server as if it was part
+# the prepared message Apprise would have otherwise put together
+#
+# Assuming our {hostname} is localhost
+# Assuming we want to include "Sound": "oceanwave" as part of the existing payload:
+apprise -vv -t "Test Message Title" -b "Test Message Body" \
+   "xml://localhost/?:Sound=oceanwave"
+```
+
+The above would post a message such as:
+```xml
+<?xml version='1.0' encoding='utf-8'?>
+<soapenv:Envelope
+    xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
+    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+    <soapenv:Body>
+        <Notification xmlns:xsi="http://nzbget.lead2gold.org/notify/NotifyXML-1.0.xsd">
+            <Version>1.0</Version>
+            <Subject>Test Message Title</Subject>
+            <MessageType>info</MessageType>
+            <Message>Test Message Body</Message>
+            <Sound>oceanwave</Sound>
+       </Notification>
+    </soapenv:Body>
+</soapenv:Envelope>
+```
+
+
 ### Header Manipulation
 Some users may require special HTTP headers to be present when they post their data to their server.  This can be accomplished by just sticking a plus symbol (**+**) in front of any parameter you specify on your URL string.
 ```bash