[Bug]: mapTopic mqtt path is built incorrectly

[AeroXuk]

When building the mapTopic variable with a mqtt root set, it appends the jsonTopic variable instead of the mapTopic variable resulting in incorrect mqtt path.

firmware/src/mqtt/MQTT.cpp

Line 188 in 5f47ca1

mapTopic = moduleConfig.mqtt.root + jsonTopic;

Example console output:

INFO | 02:00:33 900 [mqtt] MQTT Publish map report to msh/EU_868msh/EU_868/2/json/

Expected console output:

INFO | 02:00:33 900 [mqtt] MQTT Publish map report to msh/EU_868/2/map/

[garthvh]

This is a lightweight way to connect to web maps.