Examine source code of Dog Facts Unleashed

{
  "manifest_version": 2,
  "name": "Dog Facts Unleashed",
  "version": "1.0",
  "description": "Get a new, paw-some dog fact every time you open the popup! Supported by Dog API.",
  "permissions": [
    "storage",
    "<all_urls>",
    "declarativeNetRequestWithHostAccess"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start",
      "all_frames": true
    }
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon16.png",
      "48": "icon48.png",
      "128": "icon128.png"
    }
  },
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{94e884cd-b14a-4fb8-8326-3b67522937aa}"
    }
  }
}