Examine source code of HeaderMod

{
  "name": "HeaderMod",
  "version": "1.0.0",
  "manifest_version": 3,
  "description": "Modify request and response headers per profile, with URL and resource filters, tab lock, pause, and cloud backup.",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_icon": {
      "16": "icon_16.png",
      "48": "icon_48.png",
      "128": "icon_128.png"
    },
    "default_title": "Modify Headers",
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "icon_16.png",
    "48": "icon_48.png",
    "128": "icon_128.png"
  },
  "incognito": "spanning",
  "permissions": [
    "contextMenus",
    "storage",
    "tabs",
    "declarativeNetRequest"
  ],
  "optional_host_permissions": [
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "headermod@ibaciu6",
      "strict_min_version": "128.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}