Examine source code of SurferStuck

{
  "manifest_version": 2,
  "name": "SurferStuck",
  "version": "2.0",
  "description": "Adds keyboard shortcuts to Homestuck.com",
  "icons": {
    "48": "sburb.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.homestuck.com/story/*",
        "https://www.homestuck.com/story",
        "https://www.homestuck2.com/story/*"
      ],
      "js": [
        "keyboardHandler.js"
      ]
    }
  ]
}