format.sh: lint github ci configuration

Update `format.sh` to run the `actionlint` tool to check for errors in
GitHub CI configuration. Both this script and the workflow to run this
tool in CI run it using docker to ensure that the same version is in
use in both places.

Signed-off-by: Russell Bryant <[email protected]>

format.sh

@@ -287,6 +287,31 @@ else
 fi
 echo 'vLLM clang-format: Done'
 
+echo 'vLLM actionlint:'
+
+DOCKER=""
+DOCKER_RUN_OPTS=""
+if command -v "docker" &>/dev/null; then
+    DOCKER="docker"
+elif command -v "podman" &>/dev/null; then
+    DOCKER="podman"
+    DOCKER_RUN_OPTS="--userns=keep-id"
+else
+    echo "Docker or Podman are not installed. Please install one if you want to lint GitHub CI configuration."
+fi
+
+actionlint() {
+    if [ -z "$DOCKER" ]; then
+        return
+    fi
+    # Ensure we use the same version of actionlint as CI
+    IMAGE="vllm/actionlint:latest"
+    ${DOCKER} build --tag "${IMAGE}" - < .github/workflows/actionlint.dockerfile
+    ${DOCKER} run --volume="${PWD}:/repo:z" --workdir=/repo "${IMAGE}" -color
+}
+
+actionlint
+echo 'vLLM actionlint: Done'
 
 if ! git diff --quiet &>/dev/null; then
     echo 'Reformatted files. Please review and stage the changes.'