[#1307] Added linnting for GHAs.

.github/workflows/scaffold-test-common.yml

@@ -189,3 +189,18 @@ jobs:
           directory: /tmp/.scaffold-coverage-html
           fail_ci_if_error: true
           token: ${{ secrets.CODECOV_TOKEN }}
+
+  scaffold-test-actions:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Check coding standards with yamllint
+        run: yamllint --config-file .scaffold/tests/.yamllint-for-gha.yml .github/workflows
+        continue-on-error: ${{ vars.DREVOPS_CI_YAMLLINT_IGNORE_FAILURE == '1' }}
+
+      - name: Check coding standards with actionlint
+        run: docker run --rm -v "${GITHUB_WORKSPACE:-.}":/app --workdir /app rhysd/actionlint:1.6.27
+        continue-on-error: ${{ vars.DREVOPS_CI_ACTIONLINT_IGNORE_FAILURE == '1' }}

.scaffold/tests/.yamllint-for-gha.yml

@@ -0,0 +1,17 @@
+# Yamllint configuration file used to check GitHub Actions configuration files. 
+extends: default
+
+rules:
+  comments:
+    min-spaces-from-content: 1
+  document-start:
+    present: false
+  empty-lines:
+    max: 1
+    max-start: 0
+    max-end: 0
+  line-length:
+    max: 255
+  truthy:
+    allowed-values: ['true', 'false']
+    check-keys: false