added documentation for mqtt 1.3 tutorial

docs/software/other/mqtt.mdx

@@ -380,3 +380,34 @@ if __name__ == '__main__':
     while client.loop() == 0:
         pass
 ```
+### Tutorial on using MQTT with version 1.3.46+
+
+Version 1.3.46+ is the first 1.3 release with MQTT and JSON fully functional on supported devices. Heltec JSON is unlikely to work reliably.
+
+One of the major changes is that the TOPICs are different from prior versions.
+`msh/1/c/ChannelName/!12345678` and
+`msh/1/json/ChannelName/!12345678`
+
+are now
+`msh/2/c/ChannelName/!12345678` and
+`msh/2/json/ChannelName/!12345678`
+Please see the documentation at the top of this topic for that.
+
+Node-RED is a free cross-platform programming tool for wiring together hardware, APIs, and online services developed originally by IBM for IOT. It is widely used for home automation by many non-professional programmers and runs well on Pi's. Node-red has many plug-in modules written by the community. I will use this platform as a practical example on how to interface with the MQTT features of Meshtastic. Everything can be done from GUI's without using command line.
+
+Step one: use http://client.meshtastic.org/ to connect to your device via usb and adjust these settings using the web GUI.
+Enable and enter network ssid/psk. Settings-->Device Config-->Network; Save.
+Set MQTT server address. Settings-->Module Config -->MQTT config; Verify Encryption Enabled is OFF. Turn JSON Output Enabled ON. Save.
+Go to Channel Editor and set uplink and downling enabled to True. Save.
+
+Step two: if you don't want to depend on JSON decoding on the device, you can decode the proto messages off-device. To do that you will need to get the .proto files from https://github.com/meshtastic/Meshtastic-protobufs. They function as a schema and are required for decoding in Node-RED. Save the files where the node-RED application can access them and note the file path of the "mqtt.proto" file.
+
+Step three: install Node-RED plug-ins to your node-RED application for an embedded mqqt server and a protobuf decoder.
+https://flows.nodered.org/node/node-red-contrib-aedes
+https://flows.nodered.org/node/node-red-contrib-protobuf
+
+Drag, drop, and wire the nodes like this. For this example, I ran node-RED on a Windows machine. Note that file paths might be specified differently on different platforms. MQTT server wild cards are usually the same. A "+" is a single level wildcard for a specific topic level. A "#" is a multiple level wildcard that can be used at the end of a topic filter. The debug messages shown are what happens when the inject button sends a json message with a topic designed to be picked up by the specified Meshtastic device and then having it resend the message by both radio and MQTT.
+
+[<img src="/documents/mqtt/NodeRedTwo.jpg" style={{zoom:'50%'}} />](/documents/mqtt/NodeRedTwo.jpg)
+[<img src="/documents/mqtt/NodeRedThree.jpg" style={{zoom:'50%'}} />](/documents/mqtt/NodeRedThree.jpg)
+[<img src="/documents/mqtt/NR_nodes.jpg" style={{zoom:'50%'}} />](/documents/mqtt/NR_nodes.jpg)