Customization of json data for mqtt_json device_tracker

The device_tracker mqtt_json require the payload to be longitude/latitude/altitude/gps_accuracy but that’s not always the payload you might receive, so it might be nice if it can be specified.
Ex. payload_json_latitude: “GPS.lat”

Case in point here where I am pulling a topic from Chirpstack

Logger: homeassistant.components.mqtt_json.device_tracker
Source: components/mqtt_json/device_tracker.py:61
Integration: mqtt_json ([documentation](https://www.home-assistant.io/integrations/mqtt_json), [issues](https://github.com/home-assistant/home-assistant/issues?q=is%3Aissue+is%3Aopen+label%3A%22integration%3A+mqtt_json%22))
First occurred: 10:26:48 (1 occurrences)
Last logged: 10:26:48

Skipping update for following data because of missing or malformatted data: {"applicationID":"15","applicationName":"Network-testing","deviceName":"AN106","deviceProfileName":"winextfieldtester","deviceProfileID":"REDACTED","devEUI":"REDACTED","rxInfo":[{"gatewayID":"REDACTED","uplinkID":"19e6f2e7-e713-4752-b8a7-859111f3e123","name":"Laird_IoTCI_HQ","rssi":-48,"loRaSNR":6,"location":{"latitude":REDACTED,"longitude":REDACTED,"altitude":5}}],"txInfo":{"frequency":868300000,"dr":1},"adr":false,"fCnt":369,"fPort":5,"data":"AAAAAAAA//8=","object":{"accuracy":0,"altitude":65535,"latitude":0,"longitude":0}}