Examine source code of Rott 13

{
  "manifest_version": 2,
  "name": "Rott 13",
  "version": "1.0",
  "description": "Easily rot13 selected text. Woof woof!",
  "icons": {
    "48": "icon.svg",
    "96": "icon.svg"
  },
  "permissions": [
    "activeTab",
    "contextMenus"
  ],
  "optional_permissions": [
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}