Examine source code of Header Tool

{
  "manifest_version": 2,
  "name": "Header Tool",
  "version": "1.0.0",
  "description": "A simple HTTP header modifier extension with JS expressions, regex URL matching, and clipboard export.",
  "author": "Lorenzo Pavesi",
  "homepage_url": "https://github.com/loreii/HeaderTool",
  "browser_specific_settings": {
    "gecko": {
      "id": "pavesilo@gmail.com",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "48": "icons/Crocodile_48.png",
    "96": "icons/Crocodile_96.png"
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "storage",
    "tabs",
    "clipboardWrite",
    "downloads",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "sidebar_action": {
    "default_title": "Header Tool",
    "default_panel": "sidebar/sidebar.html",
    "default_icon": {
      "20": "icons/Crocodile_20.png",
      "48": "icons/Crocodile_48.png"
    }
  },
  "browser_action": {
    "default_icon": {
      "20": "icons/Crocodile_20.png",
      "48": "icons/Crocodile_48.png"
    },
    "default_title": "Header Tool",
    "default_popup": "popup/popup.html"
  },
  "commands": {
    "_execute_sidebar_action": {
      "suggested_key": {
        "default": "F4"
      }
    }
  }
}