Examine source code of My H2 Checker

{
  "manifest_version": 2,
  "name": "H2 Checker",
  "version": "1.0",
  "description": "Highlight all H2 headings on a webpage.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "script.js"
      ],
      "css": [
        "styles.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{013944c6-29d2-43d1-83a0-7afb7325f660}"
    }
  }
}