feat: add support for enterprise-level GitHub Apps

.gitignore

@@ -1,3 +1,4 @@
 .env
 coverage
 node_modules/
+.DS_Store

README.md

@@ -195,6 +195,28 @@ jobs:
           body: "Hello, World!"
 ```
 
+### Create a token for an enterprise installation
+
+```yaml
+on: [workflow_dispatch]
+
+jobs:
+  hello-world:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/create-github-app-token@v3
+        id: app-token
+        with:
+          client-id: ${{ vars.APP_CLIENT_ID }}
+          private-key: ${{ secrets.PRIVATE_KEY }}
+          enterprise: my-enterprise-slug
+      - name: Call enterprise management REST API with gh
+        run: |
+          gh api /enterprises/my-enterprise-slug/apps/installable_organizations
+        env:
+          GH_TOKEN: ${{ steps.app-token.outputs.token }}
+```
+
 ### Create a token with specific permissions
 
 > [!NOTE]
@@ -356,6 +378,13 @@ steps:
 > [!NOTE]
 > If `owner` is set and `repositories` is empty, access will be scoped to all repositories in the provided repository owner's installation. If `owner` and `repositories` are empty, access will be scoped to only the current repository.
 
+### `enterprise`
+
+**Optional:** The slug version of the enterprise name to generate a token for enterprise-level app installations.
+
+> [!NOTE]
+> The `enterprise` input is mutually exclusive with `owner` and `repositories`. GitHub Apps can be installed on enterprise accounts with permissions that let them call enterprise management APIs. Enterprise installations do not grant access to organization or repository resources.
+
 ### `permission-<permission name>`
 
 **Optional:** The permissions to grant to the token. By default, the token inherits all of the installation's permissions. We recommend to explicitly list the permissions that are required for a use case. This follows GitHub's own recommendation to [control permissions of `GITHUB_TOKEN` in workflows](https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/controlling-permissions-for-github_token). The documentation also lists all available permissions, just prefix the permission key with `permission-` (e.g., `pull-requests` → `permission-pull-requests`).

action.yml

@@ -21,6 +21,9 @@ inputs:
   repositories:
     description: "Comma or newline-separated list of repositories to install the GitHub App on (defaults to current repository if owner is unset)"
     required: false
+  enterprise:
+    description: "The slug version of the enterprise name for enterprise-level app installations (cannot be used with 'owner' or 'repositories')"
+    required: false
   skip-token-revoke:
     description: "If true, the token will not be revoked when the current job is complete"
     required: false