chore: add readme example

README.md

@@ -1 +1,15 @@
 # checkout
+
+```yaml
+uses: actions/checkout:1.0.0
+with:
+  # The path to the repository to checkout. Must be accessible with the pipeline
+  # token on publiclly
+  repository: ${{ github.server_url }}/${{ github.repository }}.git
+  # Relative path under $GITHUB_WORKSPACE to place the repository
+  path: .
+  # The branch, tag or SHA to checkout. When checking out the repository that
+  # triggered a workflow, this defaults to the reference or SHA for that event.
+  # Otherwise, uses the default branch.
+  ref: ${{ github.ref || github.sha }}
+```