Examine source code of twiffs

{
  "manifest_version": 2,
  "name": "twiffs",
  "version": "1.0",
  "description": "edited tweet history diff highlighting ➕➖",
  "icons": {
    "48": "icons/logo.svg",
    "96": "icons/logo.svg",
    "128": "icons/logo.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "twiffs@mmyron.com"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://twitter.com/*"
      ],
      "js": [
        "script.js"
      ],
      "css": [
        "style.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": [
    "tabs",
    "https://twitter.com/*"
  ]
}