Examine source code of Screen Flex

{
  "manifest_version": 3,
  "name": "Screen Flex",
  "version": "1.0.0",
  "description": "Resize your browser, preview any page in realistic device frames, capture screenshots and screen recordings. Built for designers, developers, and QA engineers.",
  "browser_specific_settings": {
    "gecko": {
      "id": "screen-flex@elesari.com",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  },
  "permissions": [
    "storage",
    "tabs",
    "scripting",
    "activeTab",
    "contextMenus",
    "declarativeNetRequestWithHostAccess",
    "webNavigation"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    },
    "default_title": "Screen Flex"
  },
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "96": "icons/icon96.png",
    "128": "icons/icon128.png"
  },
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": true
  },
  "sidebar_action": {
    "default_panel": "popup/popup.html?panel=1",
    "default_title": "Screen Flex",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png"
    }
  },
  "background": {
    "scripts": [
      "devices.js",
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "frame-element-spoofer-loader.js"
      ],
      "all_frames": true,
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "devices/*.png",
        "simulator/*",
        "viewport-tester/*",
        "devices.js",
        "frame-element-spoofer-main.js"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ]
}