Examine source code of AutoDownVote.SE

{
  "manifest_version": 2,
  "name": "AutoDownVote.SE",
  "version": "2.2resigned1",
  "license": "MPL-2.0",
  "default_locale": "en_US",
  "description": "AutoDownVote.SE is a lightweight WebExtension for Chrome and Firefox that automatically serial-downvotes questions and answers on Stack Exchange websites.",
  "icons": {
    "48": "icons/downvote-48-antialiased.png",
    "96": "icons/downvote-96-antialiased.png"
  },
  "applications": {
    "gecko": {
      "id": "AutoDownVoteSE@narawagames.appspot.com",
      "strict_min_version": "45.0"
    }
  },
  "permissions": [
    "*://*.stackexchange.com/*",
    "*://*.stackoverflow.com/*",
    "*://*.serverfault.com/*",
    "*://*.superuser.com/*",
    "*://*.mathoverflow.net/*",
    "*://*.askubuntu.com/*",
    "*://*.stackapps.com/*",
    "storage"
  ],
  "browser_action": {
    "default_icon": {
      "18": "icons/toolbar-button-18.png",
      "36": "icons/toolbar-button-18.png"
    },
    "default_title": "AutoDownVote.SE",
    "default_popup": "popup/popup.html"
  }
}