Add an action to lint other workflow files (#82)

.github/workflows/lint-actions.yml

@@ -0,0 +1,15 @@
+name: Lint GitHub Actions workflows
+on: [push, pull_request]
+
+jobs:
+  actionlint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Download actionlint
+        id: get_actionlint
+        run: bash <(curl https://raw.githubusercontent.com/rhysd/actionlint/main/scripts/download-actionlint.bash)
+        shell: bash
+      - name: Check workflow files
+        run: ${{ steps.get_actionlint.outputs.executable }} -color
+        shell: bash