Add documentation for the new met_eireann integration (#14347)

Co-authored-by: Klaas Schoute <klaas_schoute@hotmail.com>
Co-authored-by: Franck Nijhof <frenck@frenck.nl>

source/_integrations/met_eireann.markdown

@@ -0,0 +1,30 @@
+---
+title: Met Éireann
+description: Instructions on how to integrate Met Éireann with Home Assistant.
+ha_category:
+  - Weather
+ha_release: 2021.5
+ha_iot_class: Cloud Polling
+ha_config_flow: true
+ha_codeowners:
+  - '@DylanGore'
+ha_domain: met_eireann
+---
+
+The Met Éireann integration uses the [Met Éireann](https://met.ie) (The Irish Meteorological Service) Public Weather Forecast API to provide current and forecasted weather data for a given location. This integration is in no way affiliated with or endorsed by Met Éireann.
+
+<div class="note">
+
+The Met Éireann API will only provide data for Ireland, the UK and a small part of northern France. For specific coverage, please see the Notes on API document available [here](https://data.gov.ie/dataset/met-eireann-weather-forecast-api/resource/027da6d5-d819-48d1-9b16-331dba169bd1).
+
+</div>
+
+{% include integrations/config_flow.md %}
+
+## Data License
+
+The data provided by Met Éireann is licensed under the Met Éireann Open Data Custom License (similar to a Creative Commons CC BY 4.0 license). A license summary and the full license are available [here](https://data.gov.ie/dataset/met-eireann-weather-forecast-api/resource/027da6d5-d819-48d1-9b16-331dba169bd1). In short, if you distribute, broadcast or make Met Éireann data available on the public internet you must give credit to Met Éireann and display their weather warnings.
+
+## Data Changes
+
+The only changes made to the data gathered from the API are the condition descriptions which are mapped to the weather conditions supported by Home Assistant.