Examine source code of Youa

{
  "name": "Youa",
  "version": "1.2",
  "description": "Ajouter Youa à Firefox",
  "icons": {
    "16": "logo_16.png",
    "48": "logo_48.png",
    "128": "logo_128.png"
  },
  "manifest_version": 2,
  "chrome_settings_overrides": {
    "search_provider": {
      "name": "Youa",
      "search_url": "https://www.youa.eu/search.php?q={searchTerms}",
      "favicon_url": "https://www.youa.eu/asset/img/logo-responsable.jpg",
      "is_default": true,
      "encoding": "UTF-8",
      "keyword": "youa"
    },
    "homepage": "https://www.youa.eu"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.youa.eu/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ]
}