Examine source code of Page Change Watcher

{
  "manifest_version": 2,
  "name": "Page Change Watcher",
  "version": "1.3.0",
  "description": "Watch any web pages in the background and get a notification when they change. Compare the whole page by default or a specific CSS selector, with preset or custom check intervals.",
  "icons": {
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "64": "icons/icon-64.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{daa28ba0-7dfc-4639-b266-4c9335fa4427}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "alarms",
    "notifications",
    "storage",
    "tabs",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "src/watch.js",
      "src/background.js"
    ]
  },
  "browser_action": {
    "default_title": "Page Change Watcher",
    "default_popup": "src/popup.html",
    "default_icon": {
      "32": "icons/icon-32.png",
      "48": "icons/icon-48.png",
      "64": "icons/icon-64.png"
    }
  }
}