Examine source code of Right Click Search

{
  "manifest_version": 2,
  "name": "Right Click Search",
  "description": "Use the context menu to search using the engines in the Firefox search settings.",
  "version": "1.1.0",
  "icons": {
    "48": "assets/img/Icon-48.png",
    "96": "assets/img/Icon-96.png"
  },
  "permissions": [
    "search",
    "contextMenus"
  ],
  "background": {
    "scripts": [
      "./assets/js/background.js"
    ]
  }
}