Examine source code of Extract All Headings

{
  "manifest_version": 2,
  "name": "Extract All Headings",
  "version": "1.0",
  "description": "Extract all H1-H6 headings from the page.",
  "icons": {
    "64": "icon64.png",
    "128": "icon128.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_title": "Extract Headings"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b7b70f74-bed1-458b-8a53-a11a70bb1229}",
      "strict_min_version": "105.0"
    }
  }
}