docs: clarify workflow_dispatch environment input

Author: Your Name

content/actions/reference/workflows-and-actions/events-that-trigger-workflows.md

@@ -1081,6 +1081,8 @@ You can configure custom-defined input properties, default input values, and req
 
 This example defines inputs called `logLevel`, `tags`, and `environment`. You pass values for these inputs to the workflow when you run it. This workflow then prints the values to the log, using the `inputs.logLevel`, `inputs.tags`, and `inputs.environment` context properties.
 
+When you use `type: environment`, GitHub shows the workflow's environment names as the available values for that input.
+
 ```yaml
 on:
   workflow_dispatch:

content/actions/reference/workflows-and-actions/workflow-syntax.md

@@ -265,6 +265,8 @@ A boolean specifying whether the input must be supplied.
 
 The value of this parameter is a string specifying the data type of the input. This must be one of: `boolean`, `choice`, `number`, `environment` or `string`.
 
+The `environment` type is a special case that lets the workflow runner present the repository's available environments as the input choices.
+
 ## `permissions`
 
 {% data reusables.actions.jobs.section-assigning-permissions-to-jobs %}