Examine source code of Estimate My Project

{
  "name": "Estimate My Project",
  "short_name": "EMP",
  "description": "Create your custom website yourself, with no experience",
  "version": "1.3.29.0",
  "manifest_version": 2,
  "icons": {
    "16": "img/logo.png",
    "32": "img/logo.png",
    "64": "img/logo.png",
    "128": "img/logo.png"
  },
  "options_page": "index.html",
  "browser_action": {
    "default_icon": {
      "16": "img/logo.png",
      "24": "img/logo.png",
      "32": "img/logo.png",
      "128": "img/logo.png"
    },
    "default_popup": "background/popup.html"
  }
}