Examine source code of Modify HTTP Headers

{
  "name": "Modify HTTP Headers",
  "version": "2.7.0",
  "description": "Add, modify or remove any request or response header.",
  "permissions": [
    "storage",
    "declarativeNetRequestWithHostAccess"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "src/config.js",
      "src/browser.js",
      "src/runtime.js",
      "src/netrequest.js",
      "src/common.js"
    ]
  },
  "options_ui": {
    "open_in_tab": true,
    "page": "pages/options/options.html"
  },
  "icons": {
    "16": "assets/icon16.png",
    "32": "assets/icon32.png",
    "48": "assets/icon48.png",
    "64": "assets/icon64.png",
    "128": "assets/icon128.png"
  },
  "manifest_version": 3,
  "browser_specific_settings": {
    "gecko": {
      "id": "{5dd83e9c-9aa1-4a4f-a899-e11076d6eebc}"
    }
  }
}