[CI] Add a github action linter.

The linter checks all action configs in the .github/workflows folder.

Author: hageboeck

.github/workflows/lint-action-files.yml

@@ -0,0 +1,11 @@
+name: 'Lint Action Configs'
+
+on:
+  pull_request:
+    branches:
+      - '**'
+    paths:
+      - '.github/workflows/**'
+
+- name: actionlint
+  uses: raven-actions/actionlint@v2