Examine source code of Set Custom Focus

{
  "author": "igorlogius",
  "browser_action": {},
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "focus": {
      "suggested_key": {
        "default": "Ctrl+Shift+F"
      }
    }
  },
  "content_scripts": [
    {
      "all_frames": true,
      "js": [
        "content-script.js"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "icons": {
    "128": "icon.png"
  },
  "manifest_version": 2,
  "name": "Set Custom Focus",
  "options_ui": {
    "open_in_tab": true,
    "page": "options.html"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "version": "1.2.3",
  "browser_specific_settings": {
    "gecko": {
      "id": "{9995edbf-8f1c-4fd8-8d45-936a2b1a9334}"
    }
  }
}