workflows: add actionlint workflow

This will help us avoid actionlint errors in the future.

.github/actionlint.yaml

@@ -0,0 +1,7 @@
+self-hosted-runner:
+  # Labels of self-hosted runner in array of strings.
+  labels: []
+# Configuration variables in array of strings defined in your repository or
+# organization. `null` means disabling configuration variables check.
+# Empty array means no configuration variable is allowed.
+config-variables: []

.github/workflows/actionlint.yml

@@ -0,0 +1,40 @@
+name: actionlint
+
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - '.github/workflows/*.ya?ml'
+  pull_request:
+    paths:
+      - '.github/workflows/*.ya?ml'
+  merge_group:
+
+concurrency:
+  group: "actionlint-${{ github.ref }}"
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+env:
+  HOMEBREW_DEVELOPER: 1
+  HOMEBREW_NO_AUTO_UPDATE: 1
+  HOMEBREW_NO_ENV_HINTS: 1
+
+jobs:
+  workflow_syntax:
+    if: github.repository_owner == 'Homebrew'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set up Homebrew
+        uses: Homebrew/actions/setup-homebrew@master
+        with:
+          test-bot: false
+
+      - uses: actions/checkout@v3
+
+      - name: Set up actionlint
+        run: |
+          brew install actionlint shellcheck
+          echo "::add-matcher::$(brew --repository)/.github/actionlint-matcher.json"
+
+      - run: actionlint