Examine source code of Clipboard Concat

{
  "description": "Concatenates selected text or link to clipboard entity",
  "manifest_version": 2,
  "name": "Clipboard Concat",
  "version": "1.0",
  "homepage_url": "https://www.google.com",
  "icons": {
    "48": "icons/48.png",
    "96": "icons/96.png"
  },
  "permissions": [
    "menus",
    "activeTab",
    "contextMenus",
    "clipboardWrite",
    "clipboardRead"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{53323020-6120-4445-b42c-ca07767be031}"
    }
  }
}