Examine source code of Twitter Print Styles

{
  "manifest_version": 2,
  "name": "Twitter Print Styles",
  "version": "2.1.5",
  "description": "Simple print styles for saving Twitter threads as PDFs.",
  "icons": {
    "16": "icon-16.png",
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "https://twitter.com/*"
      ],
      "css": [
        "index.css"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{eb2aab60-c1c5-4b9f-88e3-ac5c63ac4616}"
    }
  }
}