Examine source code of Always Pinned

{
  "manifest_version": 2,
  "name": "Always Pinned",
  "version": "0.0.3",
  "browser_specific_settings": {
    "gecko": {
      "id": "{274e217d-2a1c-4bdf-84fd-2a02c1b64a5f}",
      "strict_min_version": "54.0"
    }
  },
  "description": "Make sure certain websites are opened & pinned on start.",
  "background": {
    "scripts": [
      "always-pinned.js"
    ]
  },
  "permissions": [
    "tabs",
    "menus",
    "storage"
  ]
}