Add an example using --strict to README.md

Author: norio-nomura

README.md

@@ -23,6 +23,10 @@ jobs:
       - uses: actions/checkout@v1
       - name: GitHub Action for SwiftLint
         uses: norio-nomura/[email protected]
+      - name: GitHub Action for SwiftLint with --strict
+        uses: norio-nomura/[email protected]
+        with:
+          args: --strict
 ```
 
 ## Secrets