infra: add github actions linter

Taken from the main checkstyle repository.

Author: Bananeweizen

.github/workflows/actionlint.yml

@@ -0,0 +1,26 @@
+name: Lint workflows of GitHub Actions
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - '.github/workflows/**'
+  pull_request:
+    branches:
+      - '*'
+    paths:
+      - '.github/workflows/**'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  actionlint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Check workflow files
+        uses: docker://rhysd/actionlint:latest