Examine source code of Heading Optimizer

{
  "manifest_version": 2,
  "name": "Heading Optimizer",
  "version": "1.1",
  "description": "A Firefox extension to optimize H1, H2, H3 headings on websites.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentScript.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8e48780a-cb5c-4289-9a9c-7694273d1a61}"
    }
  }
}