Examine source code of ffally

{
  "manifest_version": 2,
  "name": "ffally",
  "version": "1.0",
  "description": "Highlights links to ally repos.",
  "icons": {
    "48": "icon.ico"
  },
  "permissions": [
    "storage",
    "https://raw.githubusercontent.com/*",
    "https://github.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "ffally.js"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{0d7696f7-9c8d-4633-a68e-da5b94542d71}"
    }
  }
}