Examine source code of Logo Switcher

{
  "manifest_version": 2,
  "name": "Logo Switcher",
  "description": "Switch logo",
  "version": "0.0.2",
  "homepage_url": "https://github.com/2chanhaeng/logo-switcher",
  "icons": {
    "16": "twitter-logo.png",
    "48": "twitter-logo.png",
    "128": "twitter-logo.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://twitter.com/*",
        "*://*.twitter.com/*"
      ],
      "css": [
        "./style.css"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{690ac073-5fdd-4f1e-a66a-9e2941e7e5b4}"
    }
  }
}