Add actionlint feature

src/actionlint/devcontainer-feature.json

@@ -0,0 +1,23 @@
+{
+  "name": "actionlint",
+  "id": "actionlint",
+  "version": "1.0.0",
+  "options": {
+    "version": {
+      "type": "string",
+      "proposals": [
+        "latest"
+      ],
+      "default": "latest",
+      "description": "Select or enter an actionlint version."
+    },
+    "installPath": {
+      "type": "string",
+      "default": "/usr/local/bin",
+      "description": "The path where actionlint will be installed."
+    }
+  },
+  "installsAfter": [
+    "ghcr.io/devcontainers/features/common-utils"
+  ]
+}

src/actionlint/install.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env sh
+
+set -e
+
+ACTIONLINT_VERSION="${VERSION:-"latest"}"
+INSTALL_PATH="${INSTALLPATH:-"/usr/local/bin"}"
+
+if [ "$(id -u)" -ne 0 ]; then
+  echo -e 'Script must be run as root. Use sudo, su, or add "USER root" to your Dockerfile before running this script.'
+  exit 1
+fi
+
+curl_installed=""
+
+if ! [ type curl >/dev/null 2>&1 ]; then
+  apt update --yes
+  apt install --no-install-recommends --yes curl ca-certificates
+
+  curl_installed="true"
+fi
+
+curl -sSL https://raw.githubusercontent.com/rhysd/actionlint/main/scripts/download-actionlint.bash | \
+  /bin/bash -s -- "${ACTIONLINT_VERSION}" "${INSTALL_PATH}"
+
+if ! [ -z $curl_installed ]; then
+  apt purge curl --autoremove --yes
+fi