Examine source code of searchmgr

{
  "name": "Search Manager Online",
  "short_name": "Search Mgr",
  "description": "Search Manager Online allow to between search engines (Yahoo / BING) directly from the new tab page",
  "default_locale": "en",
  "icons": {
    "16": "/content/images/icons/16.png",
    "48": "/content/images/icons/48.png",
    "128": "/content/images/icons/128.png"
  },
  "background": {
    "page": "background.html",
    "persistent": true
  },
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "chrome_settings_overrides": {
    "search_provider": {
      "encoding": "UTF-8",
      "favicon_url": "https://searchmgr.online/?favicon",
      "is_default": true,
      "keyword": "MSM",
      "name": "Search Manager Online",
      "search_url": "https://searchmgr.online/search/?s={searchTerms}",
      "suggest_url": "https://searchmgr.online/search/?s={searchTerms}"
    }
  },
  "manifest_version": 2,
  "permissions": [
    "*://*.searchmgr.online/*",
    "tabs"
  ],
  "version": "1.1.3",
  "applications": {
    "gecko": {
      "strict_min_version": "54.0"
    }
  }
}