I hope to add applicable scenarios for the modbus_reply() function.

[SupermanOfHeiLinPu]

I want to write a Modbus slave software, but my register layout is as follows: [0, 5]: Input registers; [6, 10]: Holding registers; [11, 15]: Input registers; [16, 20]: Holding registers. In this case, the provided modbus_mapping_t and modbus_reply() functions in the library cannot achieve this functionality. I think we can write another modbus_reply() function that uses a callback mechanism to retrieve and set data.