Added sinch component (home-assistant/core#26502)

source/_components/sinch.markdown

@@ -0,0 +1,64 @@
+---
+title: "Sinch SMS"
+description: "Instructions on how to add Sinch notifications to Home Assistant."
+logo: sinch.png
+ha_category:
+  - Notifications
+ha_release: 0.99.1
+redirect_from:
+ - /components/notify.sinch/
+---
+
+The `sinch` platform uses [Sinch](https://www.sinch.com/products/messaging/sms/) to deliver notifications from Home Assistant.
+
+## Prerequisites
+
+Go to your [Sinch Dashboard](https://dashboard.sinch.com/sms/api/rest) and click "Add new REST API". You should now be able to obtain your `service_plan_id` and `api_key`.
+
+## Configuration
+
+To add Sinch to your installation, add the following to your Home Assistant `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+notify:
+  - platform: sinch
+    name: Sinch
+    service_plan_id: SINCH_SERVICE_PLAN_ID
+    api_key: SINCH_API_KEY
+
+# Using default recipients
+notify:
+  - platform: sinch
+    name: Sinch
+    service_plan_id: SINCH_SERVICE_PLAN_ID
+    api_key: SINCH_API_KEY
+    default_recipient: [PHONE_NO1, PHONE_NO2]
+```
+
+```
+{% configuration %}
+name:
+  description: "Setting the optional parameter name allows multiple notifiers to be created. The default value is `Sinch`. The notifier will bind to the service `notify.NOTIFIER_NAME`."
+  required: false
+  type: string
+service_plan_id:
+  description: Your Sinch Service Plan ID.
+  required: true
+  type: string
+api_key:
+  description: Your API Token.
+  required: true
+  type: string
+default_recipient:
+  description: "A single or multiple phone numbers. This is where you want to send your SMS notification messages by default (when not specifying `target` in the service call), e.g., `09171234567` or `[09171234567, 09177654321]`."
+  required: false
+  type: [string, list]
+sender:
+  description: The name or number of the sender.
+  required: false
+  type: string
+  default: 'Home Assistant'
+{% endconfiguration %}
+```
+To use notifications, please see the [getting started with automation page](/getting-started/automation/).