Add support for HACS (#8)

* Create hacs.json

* Create info.md

hacs.json

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+{
+  "name": "Shellies Discovery Gen2",
+  "homeassistant": "2021.12.0",
+  "zip_release": true,
+  "filename": "shellies-discovery-gen2.zip"
+}

info.md

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+[![Community Forum][forum-shield]][forum]  [![Buy me a coffee][buy-me-a-coffee-shield]][buy-me-a-coffee]  [![PayPal_Me][paypal-me-shield]][paypal-me]
+
+This script adds MQTT discovery support for Shelly Gen2 devices in the [Home Assistant](https://home-assistant.io/).
+
+![image](https://user-images.githubusercontent.com/478555/151068134-eac574ac-60c9-4e19-8ff1-cefa5046177d.png)
+
+## Prerequisites
+
+This script needs Home Assistant `python_script` component so, if you never used it, I strongly suggest you to follow the [official instruction](https://www.home-assistant.io/integrations/python_script#writing-your-first-script) and check that `python_script` is properly configured and it's working.
+
+For the device to work with the script, it must have MQTT configured and options `RPC status notifications over MQTT` and `Generic status update over MQTT` enabled.
+
+## Installation
+
+You can download `shellies_discovery_gen2.py` file and save it in `<config>/python_scripts` folder.
+
+## Supported devices
+
+- Shelly Plus 1
+- Shelly Plus 1PM
+- Shelly Plus i4
+- Shelly Pro 1
+- Shelly Pro 1PM
+- Shelly Pro 2
+- Shelly Pro 2PM
+- Shelly Pro 4PM
+
+## How to debug
+
+To debug the script add this to your `logger` configuration:
+
+```yaml
+# configuration.yaml file
+logger:
+  default: warning
+  logs:
+    homeassistant.components.python_script: debug
+    homeassistant.components.automation: info
+```
+
+## Supported platforms
+
+- switch
+- light
+- sensor
+
+## Supported features
+
+- the device name is taken from the device configuration
+- the relay name is taken from the device configuration
+- the relay consumption type is taken from the device configuration
+- if the input type is set to button, device automation triggers are available
+- custom MQTT prefixes are supported
+
+## Known problems
+
+- availability doesn’t work (firmware change is needed)
+
+## Script arguments
+
+key | optional | type | default | description
+-- | -- | -- | -- | --
+`discovery_prefix` | True | string | `homeassistant` | MQTT discovery prefix
+`qos` | True | integer | `0` | MQTT QoS, you can use `0`, `1` or `2`
+
+## Minimal configuration
+
+```yaml
+# configuration.yaml file
+python_script:
+
+# automations.yaml file
+- id: shellies_announce_gen2
+  alias: "Shellies Announce Gen2"
+  trigger:
+    - platform: homeassistant
+      event: start
+  variables:
+    device_info_payload:  "{{ {'id': 1, 'src':'shellies_discovery', 'method':'Shelly.GetConfig'} | to_json }}"
+  action:
+    - service: mqtt.publish
+      data:
+        topic: "shellypro4pm-aabbcc/rpc"  # shellypro4pm-aabbccddeeff is a device ID
+        payload: "{{ device_info_payload }}"
+    - service: mqtt.publish
+      data:
+        topic: "shellyplus1pm-112233/rpc"  # shellyplus1pm-112233445566 is a device ID
+        payload: "{{ device_info_payload }}"
+
+- id: shellies_discovery_gen2
+  alias: "Shellies Discovery Gen2"
+  mode: queued
+  max: 999
+  trigger:
+  - platform: mqtt
+    topic: shellies_discovery/rpc
+  action:
+  - service: python_script.shellies_discovery_gen2
+    data:
+      id: "{{ trigger.payload_json.src }}"
+      device_config: "{{ trigger.payload_json.result }}"
+```
+
+[forum]: https://community.home-assistant.io/t/shellies-discovery-gen2-script/384479
+[forum-shield]: https://img.shields.io/badge/community-forum-brightgreen.svg?style=popout
+[buy-me-a-coffee-shield]: https://img.shields.io/static/v1.svg?label=%20&message=Buy%20me%20a%20coffee&color=6f4e37&logo=buy%20me%20a%20coffee&logoColor=white
+[buy-me-a-coffee]: https://www.buymeacoffee.com/QnLdxeaqO
+[paypal-me-shield]: https://img.shields.io/static/v1.svg?label=%20&message=PayPal.Me&logo=paypal
+[paypal-me]: https://www.paypal.me/bieniu79