Examine source code of PaperSpan

{
  "description": "Read It Later app to read more and finish your reading list - to use the web for better you.",
  "manifest_version": 3,
  "name": "PaperSpan",
  "version": "1.2",
  "homepage_url": "https://www.paperspan.com/",
  "icons": {
    "16": "icons/icon-16.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "firefox@paperspan.com",
      "strict_min_version": "109.0"
    }
  },
  "permissions": [
    "activeTab",
    "tabs",
    "identity",
    "storage",
    "menus"
  ],
  "host_permissions": [
    "http://*/*",
    "https://*/*"
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "icons/icon-16.png",
        "icons/icon-48.png",
        "icons/icon-128.png",
        "css/toastr.css",
        "js/toastr.js"
      ],
      "matches": [
        "http://*/*",
        "https://*/*"
      ]
    }
  ],
  "action": {
    "default_icon": {
      "19": "icons/icon-19.png",
      "38": "icons/icon-38.png"
    },
    "default_title": "Add To PaperSpan",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "js/jquery-3.3.1.min.js",
        "js/browser-polyfill.min.js",
        "js/toastr.js",
        "js/content_script.js"
      ],
      "css": [
        "css/toastr.css"
      ],
      "run_at": "document_start"
    }
  ],
  "background": {
    "scripts": [
      "js/browser-polyfill.min.js",
      "js/background.js"
    ]
  },
  "options_ui": {
    "page": "options.html"
  }
}