Examine source code of API Status Checker

{
  "manifest_version": 2,
  "name": "API Status Checker",
  "version": "1.0",
  "description": "Displays API status when loading a webpage.",
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_title": "API Status",
    "default_popup": "popup.html"
  },
  "icons": {
    "128": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c949ef4b-24e0-4d94-9f95-b3ac699e2f5a}"
    }
  }
}