Examine source code of Header Tags Copier

{
  "manifest_version": 2,
  "name": "Header Tag Copier",
  "version": "1.9",
  "description": "Copy all header tags (h1-h6) to clipboard",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab",
    "clipboardWrite",
    "notifications"
  ],
  "browser_action": {
    "default_icon": "icon.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentScript.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{512d0b4c-f507-4602-9bff-059784304340}"
    }
  }
}