export limit growatt mic

working with a MIC 750 TL-X (which happens to generate a bit more 8)) with the below config. and yes, 
this works fine along with the sensors of the platform growatt_solar.

```yaml
uart:
  tx_pin: GPIO4
  rx_pin: GPIO5
  baud_rate: 9600

modbus:

modbus_controller:
  - id: modbus_gw750
  
sensor:
  - platform: modbus_controller
    modbus_controller_id: modbus_gw750
#    
#  sensor returning the currently set limit read from the register for showing it in HA
#
    name: "Limit %" 
    id: gw750_limit_set
    register_type: holding
    address: 3
    unit_of_measurement: "%"
    value_type: U_WORD

number:
  - platform: modbus_controller
    modbus_controller_id: modbus_gw750
#
#  creating a number entity and it's corresponding slider in HA
#  and writes it to the register on change
#
    name: GW750 Limit
    id: gw750_limit
    address: 3
    register_type: holding
    value_type: U_WORD
    min_value: 10
    max_value: 100
    step: 1
    ```