Examine source code of Gmail Copier

{
  "manifest_version": 2,
  "name": "Gmail Copier",
  "version": "1.2",
  "description": "Copie l'adresse e-mail, la date et le corps du texte d'un mail sous Gmail",
  "permissions": [
    "activeTab",
    "contextMenus",
    "tabs",
    "clipboardWrite",
    "https://mail.google.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "48": "icones/icons8-copie-24.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "gmailcopier@example.com"
    }
  }
}