Examine source code of Customizable Shortcuts

{
  "manifest_version": 2,
  "name": "Customizable Shortcuts",
  "version": "1.0",
  "description": "Assign easy shortcuts for favorite sites.",
  "permissions": [
    "storage",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "commands": {
    "open-site-1": {
      "suggested_key": {
        "default": "Ctrl+Shift+1"
      },
      "description": "Open favorite site 1"
    },
    "open-site-2": {
      "suggested_key": {
        "default": "Ctrl+Shift+2"
      },
      "description": "Open favorite site 2"
    }
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{4e41b58f-89b7-402c-a133-4aea097c30fe}"
    }
  }
}