Examine source code of ReduceThis

{
  "manifest_version": 3,
  "name": "ReduceThis",
  "version": "1.0",
  "description": "A Firefox extension to change selected DOM text on a website to new text.",
  "permissions": [
    "activeTab",
    "contextMenus",
    "scripting",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{12345678-abcd-1234-ef00-1234567890ab}",
      "strict_min_version": "58.0"
    }
  },
  "host_permissions": [
    "http://localhost/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon16.png",
      "128": "icons/icon16.png"
    }
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon16.png",
    "128": "icons/icon16.png"
  }
}