Add documentation for set_options service call (#3292)

* Add documentation for set_options service call

* Minor changes

source/_components/input_select.markdown

@@ -37,7 +37,7 @@ Configuration variables:
 
 - **[alias]** array (*Required*): Alias for the input. Multiple entries are allowed..
   - **name** (*Optional*): Friendly name of the input.
-  - **options** array  (*Required*): List of options to choose from.
+  - **options** array (*Required*): List of options to choose from.
   - **initial** (*Optional*): Initial value when Home Assistant starts.
   - **icon** (*Optional*): Icon for entry.
 
@@ -71,6 +71,22 @@ automation:
           option: Paulus
 ```
 
+To dynamically set the `input_select` options you can call `input_select.set_options`. The following example can be used in an automation rule:
+
+```yaml
+# Example configuration.yaml entry
+automation:
+  - alias: example automation
+    trigger:
+      platform: event
+      event_type: MY_CUSTOM_EVENT
+    action:
+      - service: input_select.set_options
+        data:
+          entity_id: input_select.who_cooks
+          options: ["Item A", "Item B", "Item C"]
+```
+
 ### {% linkable_title Scenes %}
 
 To specify a target option in a [Scene](/components/scene/) you have to specify the target as `option` attribute: