Use latest version of checkout action (#30)

Author: jeffwidman

README.md

@@ -51,7 +51,7 @@ jobs:
   lintAllTheThings:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
     - name: yaml-lint
       uses: ibiqlik/action-yamllint@v3
 ```