Modbus feature for Register 141 is incomplete: proposal

[hutchwilco]

Hi
Enjoying this integration thank you.
I have a 3 phase HV hybrid 40kW Deye.

I found that the functions I need to set in the inverter workmode are not implemented by this code, however I'm unsure about the best way to pull request or propose the solution.

Currently the code in work_mode.yaml allows for register 141 in two places:
`select:

• platform: modbus_controller
  id: energy_management_priority
  use_write_multiple: true
  modbus_controller_id: ${modbus_controller_id}
  name: "Energy Management Priority"
  address: 141
  value_type: U_WORD
  icon: "mdi:priority-high"
  optionsmap:
  "Battery First": 0
  "Load First": 1`

also

`switch:

• platform: modbus_controller
  use_write_multiple: true
  modbus_controller_id: ${modbus_controller_id}
  register_type: holding
  name: "Load Priority"
  bitmask: 1
  address: 141
  icon: "mdi:priority-high"`

However, the modbus documentation for this inverter suggests that are four modes to configure on this register. Some of these might help solve my actual problem which is phase balancing on External CT reference.

Also another problem is the configuration above- I believe "select" will overwrite all bits on the register, instead of leaving the other bits as is. Is this correct?

My proposed additions are:

`switch:

• platform: modbus_controller
  use_write_multiple: true
  modbus_controller_id: ${modbus_controller_id}
  register_type: holding
  name: "Passive Grid Power Balance"
  id: passive_grid_power_balance
  bitmask: 12
  address: 141
  icon: "mdi:transmission-tower"

• platform: modbus_controller
  use_write_multiple: true
  modbus_controller_id: ${modbus_controller_id}
  register_type: holding
  name: "Active Grid Power Balance"
  id: active_grid_power_balance
  bitmask: 48
  address: 141
  icon: "mdi:transmission-tower-export"`

Please let me know if I have any misunderstandings. I would really like to support these features.

Thanks