Examine source code of TFS Dark

{
  "manifest_version": 2,
  "name": "TFS Dark",
  "version": "1.0",
  "description": "Adds a dark theme to all webpages with /tfs/ in their path.",
  "icons": {
    "48": "icons/tfsdark.png"
  },
  "applications": {
    "gecko": {
      "id": "benjyring@gmail.com"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://*/tfs/*"
      ],
      "js": [
        "tfsdark.js"
      ]
    }
  ]
}