Examine source code of Cartoon Timer

{
  "manifest_version": 2,
  "name": "Cartoon Timer",
  "version": "1.0",
  "description": "Set a timer for your kid to watch websites like YouTube. Automatically blocks access when time is up.",
  "permissions": [
    "storage",
    "tabs",
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8fc7ba6a-1c7e-4da5-93a4-0e9f273645ca}"
    }
  }
}