Examine source code of Quick Peek for Firefox

{
  "name": "Quick Peek for Firefox",
  "version": "0.0.3",
  "short_name": "Quick Peek",
  "manifest_version": 2,
  "permissions": [
    "<all_urls>",
    "tabs",
    "contextMenus",
    "webNavigation"
  ],
  "background": {
    "scripts": [
      "/background.js"
    ]
  }
}