Examine source code of HeadingsMap

{
  "name": "__MSG_extensionName__",
  "description": "__MSG_extensionDescription__",
  "author": "Jorge Rumoroso",
  "manifest_version": 2,
  "version": "4.10.7",
  "icons": {
    "48": "icons/headingsMap48.png",
    "128": "icons/headingsMap128_with_margin.png"
  },
  "default_locale": "en",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_scripts/headingsmap.js"
      ],
      "css": [
        "css/inDocumentStyles.css"
      ],
      "run_at": "document_end",
      "all_frames": true
    }
  ],
  "background": {
    "scripts": [
      "service-worker.js"
    ]
  },
  "permissions": [
    "<all_urls>",
    "activeTab",
    "storage",
    "webNavigation"
  ],
  "browser_action": {
    "default_icon": {
      "48": "icons/headingsMap48.png"
    },
    "default_title": "headingsMap"
  },
  "web_accessible_resources": [
    "html/*",
    "css/*",
    "getFrameId",
    "_locales/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "headings@niquelheadings.net",
      "strict_min_version": "58.0"
    },
    "gecko_android": {
      "strict_min_version": "79.0"
    }
  }
}