Examine source code of Leboncoin Immo

{
  "manifest_version": 2,
  "name": "Leboncoin Immo",
  "version": "1.2resigned1",
  "description": "Affiche le prix/m^2 sur la page de détail des annonces immobilières.",
  "icons": {
    "48": "icons/fr.leboncoin.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.leboncoin.fr/ventes_immobilieres/*.htm"
      ],
      "js": [
        "display_price_ratio.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{00687d4a-588a-4c5d-8888-a8ce9d3e4131}"
    }
  }
}