Examine source code of NanoGift

{
  "manifest_version": 2,
  "name": "NanoGift",
  "version": "1.3",
  "icons": {
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "description": "Tip nano",
  "background": {
    "scripts": [
      "background/nanogift.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_icon": "icons/icon-32.png",
    "theme_icons": [
      {
        "light": "icons/icon-32.png",
        "dark": "icons/icon-32.png",
        "size": 32
      }
    ],
    "default_title": "NanoGift",
    "default_popup": "popup/tip.html"
  },
  "permissions": [
    "<all_urls>",
    "tabs",
    "webRequest",
    "clipboardWrite",
    "webNavigation"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "content/youtube.js"
      ],
      "run_at": "document_end"
    }
  ]
}