Examine source code of @ Search Shortcuts

{
  "manifest_version": 2,
  "name": "Search shortcuts",
  "version": "1.1",
  "description": "Define custom shortcuts for websites to search",
  "icons": {
    "48": "./icons/add-search-engine-24.svg",
    "96": "./icons/add-search-engine-24.svg"
  },
  "omnibox": {
    "keyword": "@"
  },
  "permissions": [
    "bookmarks",
    "tabs"
  ],
  "page_action": {
    "browser_style": true,
    "default_icon": "./icons/add-search-engine-24.svg",
    "show_matches": [
      "https://*/*",
      "http://*/*"
    ],
    "default_title": "add @ search keyword",
    "default_popup": "popup/index.html"
  },
  "background": {
    "scripts": [
      "search.js"
    ]
  }
}