Examine source code of Multi Sites Viewer

{
  "manifest_version": 2,
  "name": "Multi Sites Viewer",
  "version": "0.5.0",
  "description": "Sites viewer for 2 different sites on the same web page",
  "icons": {
    "48": "app_icon_48.png",
    "128": "app_icon_128.png"
  },
  "browser_action": {
    "default_icon": "app_icon_128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "applications": {
    "gecko": {
      "id": "info@eggsystems.jp",
      "strict_min_version": "60.0"
    }
  },
  "permissions": [
    "storage",
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ]
}