Examine source code of API Request Tester

{
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "version": "1.0",
  "description": "__MSG_extensionDescription__",
  "icons": {
    "48": "icons/icon.png"
  },
  "browser_action": {
    "default_icon": {
      "48": "icons/icon.png"
    },
    "default_title": "Web Dev Toolbox",
    "default_popup": "popup/popup.html"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{c200f2f0-ba70-46b2-b921-ccdf699fb2d1}"
    }
  }
}