docs: add example usage to license_check (#164)

Author: alestiago

site/docs/workflows/license_check.md

@@ -72,3 +72,31 @@ The allowed and forbidden options can't be used at the same time. If you want to
 **Optional** Disregard licenses that failed to be retrieved.
 
 **Default** `false`
+
+## Example Usage
+
+```yaml
+name: license_check
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+on:
+  pull_request:
+    paths:
+      - 'pubspec.yaml'
+      - '.github/workflows/license_check.yaml'
+  push:
+    branches:
+      - main
+    paths:
+      - 'pubspec.yaml'
+      - '.github/workflows/license_check.yaml'
+
+jobs:
+  license_check:
+    uses: VeryGoodOpenSource/very_good_workflows/.github/workflows/license_check.yml@v1
+    with:
+      allowed: 'MIT,BSD-3-Clause,BSD-2-Clause,Apache-2.0'
+```