[MQTT] Design and document topic hierarchy in config.json

[ezehf2]

Create a config.json file in the root of the repository that stores the broker address, port number, and the full topic structure for all sensor types across all rooms. Topics should follow the pattern campus/roomXXX/sensortype — for example campus/room101/temperature. All team members must read from this file rather than hardcoding values in their own scripts. Once created, document the structure in the README so everyone understands how to use it.