Examine source code of Simple Auto Refresher

{
  "manifest_version": 2,
  "name": "Simple Auto Refresher",
  "browser_specific_settings": {
    "gecko": {
      "id": "mawlaariful@gmail.com",
      "strict_min_version": "60.0"
    }
  },
  "version": "1.0.2",
  "description": "A simple tool to make the website live every time! Refresh your pages with selected time interval.",
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "browser_action": {
    "default_icon": "icon16.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "*://*.gumroad.com/*",
    "activeTab",
    "storage",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "popup.js"
      ]
    }
  ]
}