Examine source code of Tweton

{
  "name": "Tweton",
  "description": "Capture tweet inspirations without leaving Twitter.",
  "version": "1.4.0",
  "manifest_version": 2,
  "browser_action": {
    "default_popup": "index.html",
    "default_title": "Open the popup"
  },
  "optional_permissions": [
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://twitter.com/*"
      ],
      "run_at": "document_end",
      "js": [
        "./index.global.js"
      ],
      "css": [
        "./style.css"
      ]
    }
  ],
  "background": {
    "page": "background.html",
    "persistent": false
  },
  "icons": {
    "128": "logo128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2c0b74ab-bffa-44ec-8e5c-94789286c323}"
    }
  }
}