Examine source code of Append Domain

{
  "manifest_version": 2,
  "name": "Append Domain",
  "author": "Richard Adenling",
  "version": "1.3resigned1",
  "description": "Appends the current domain name to the tab title.",
  "homepage_url": "https://github.com/radenling/append-domain",
  "content_scripts": [
    {
      "matches": [
        "*://*/*",
        "file:///*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{462b2b0a-87e2-4da8-8c79-c2701a3a1d5b}"
    }
  }
}