Examine source code of Lazy Helpers

{
  "manifest_version": 2,
  "name": "Lazy Helpers",
  "description": "Permenant Youtube play",
  "version": "1.5",
  "homepage_url": "https://github.com/mdn/webextensions-examples/tree/master/page-to-extension-messaging",
  "icons": {
    "48": "icons/message-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://*/*"
      ],
      "js": [
        "./dist/bundle.js"
      ]
    }
  ]
}