Add documentation for Niko smart plug 552-80698 (Koenkk#1605)

* Add documentation for Niko smart plug 552-80698

* Swap device image from PNG to JPG

Author: ldekamps

docs/devices/552-80698.md

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+---
+title: "Niko 552-80698 control via MQTT"
+description: "Integrate your Niko 552-80698 via Zigbee2MQTT with whatever smart home infrastructure you are using without the vendor's bridge or gateway."
+addedAt: 2022-09-25T09:46:05.921Z
+pageClass: device-page
+---
+
+<!-- !!!! -->
+<!-- ATTENTION: This file is auto-generated through docgen! -->
+<!-- You can only edit the "Notes"-Section between the two comment lines "Notes BEGIN" and "Notes END". -->
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+
+# Niko 552-80698
+
+|     |     |
+|-----|-----|
+| Model | 552-80698  |
+| Vendor  | Niko  |
+| Description | Smart plug with side earthing pin |
+| Exposes | switch (state), power, energy, power_on_behavior, linkquality |
+| Picture | ![Niko 552-80698](https://www.zigbee2mqtt.io/images/devices/552-80698.jpg) |
+
+
+<!-- Notes BEGIN: You can edit here. Add "## Notes" headline if not already present. -->
+
+
+<!-- Notes END: Do not edit below this line -->
+
+
+## Options
+*[How to use device type specific configuration](../guide/configuration/devices-groups.md#specific-device-options)*
+
+* `power_calibration`: Calibrates the power value (percentual offset), takes into effect on next report of device. The value must be a number.
+
+* `current_calibration`: Calibrates the current value (percentual offset), takes into effect on next report of device. The value must be a number.
+
+* `voltage_calibration`: Calibrates the voltage value (percentual offset), takes into effect on next report of device. The value must be a number.
+
+
+## Exposes
+
+### Switch 
+The current state of this switch is in the published state under the `state` property (value is `ON` or `OFF`).
+To control this switch publish a message to topic `zigbee2mqtt/FRIENDLY_NAME/set` with payload `{"state": "ON"}`, `{"state": "OFF"}` or `{"state": "TOGGLE"}`.
+To read the current state of this switch publish a message to topic `zigbee2mqtt/FRIENDLY_NAME/get` with payload `{"state": ""}`.
+
+### Power (numeric)
+Instantaneous measured power.
+Value can be found in the published state on the `power` property.
+To read (`/get`) the value publish a message to topic `zigbee2mqtt/FRIENDLY_NAME/get` with payload `{"power": ""}`.
+It's not possible to write (`/set`) this value.
+The unit of this value is `W`.
+
+### Energy (numeric)
+Sum of consumed energy.
+Value can be found in the published state on the `energy` property.
+To read (`/get`) the value publish a message to topic `zigbee2mqtt/FRIENDLY_NAME/get` with payload `{"energy": ""}`.
+It's not possible to write (`/set`) this value.
+The unit of this value is `kWh`.
+
+### Power_on_behavior (enum)
+Controls the behaviour when the device is powered on.
+Value can be found in the published state on the `power_on_behavior` property.
+To read (`/get`) the value publish a message to topic `zigbee2mqtt/FRIENDLY_NAME/get` with payload `{"power_on_behavior": ""}`.
+To write (`/set`) a value publish a message to topic `zigbee2mqtt/FRIENDLY_NAME/set` with payload `{"power_on_behavior": NEW_VALUE}`.
+The possible values are: `off`, `previous`, `on`.
+
+### Linkquality (numeric)
+Link quality (signal strength).
+Value can be found in the published state on the `linkquality` property.
+It's not possible to read (`/get`) or write (`/set`) this value.
+The minimal value is `0` and the maximum value is `255`.
+The unit of this value is `lqi`.
+