Examine source code of Alex Filter

{
  "name": "AK Filter",
  "description": "Operate Google Spreadsheet Filter with Keyboard Shortcut",
  "version": "0.2resigned1",
  "icons": {
    "16": "funnel16.png",
    "48": "funnel64.png",
    "128": "funnel128.png"
  },
  "browser_action": {
    "default_icon": "funnel16.png",
    "default_popup": "popup.html",
    "default_title": "AK Filter: One Easy Thing Google Should've Done"
  },
  "manifest_version": 2,
  "content_scripts": [
    {
      "matches": [
        "https://docs.google.com/spreadsheets/d/*"
      ],
      "css": [
        "reform.css"
      ],
      "js": [
        "simplify.js"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ba51a074-320a-43ea-8ef7-e4374ae857d9}"
    }
  }
}