Examine source code of Send to X4

{
  "manifest_version" : 3 ,
  "name" : "Send to X4",
  "version" : "1.2.3",
  "author": "Xatpy",
  "description" : "Send articles from any website to Xteink X4 e-ink reader as EPUB",
  "permissions" : [
    "scripting" ,
    "activeTab" ,
    "downloads" ,
    "tabs" ,
    "storage" 
  ],
  "host_permissions" : [
    "http://192.168.3.3/*" ,
    "http://192.168.4.1/*" ,
    "http://192.168.1.224/*" ,
    "<all_urls>" 
  ],
  "background" : {
    "scripts" : [
      "src/epub/jszip.min.js" ,
      "src/utils/logger.js" ,
      "src/utils/sanitize.js" ,
      "src/utils/transfer_utils.js" ,
      "src/utils/folder_path.js" ,
      "src/epub/epub_templates.js" ,
      "src/epub/epub_builder.js" ,
      "src/upload/x4_upload_tab.js" ,
      "src/upload/crosspoint_upload.js" ,
      "src/utils/settings.js" ,
      "src/background/service_worker.js" 
    ]
  },
  "content_scripts" : [
    {
      "matches" : [
        "https://*/*" ,
        "http://*/*" 
      ],
      "exclude_matches" : [
        "http://192.168.3.3/*",
        "http://192.168.4.1/*",
        "http://192.168.1.224/*"
      ],
      "js" : [
        "src/content/readability.min.js" 
      ],
      "run_at" : "document_idle" 
    }
  ],
  "action" : {
    "default_title" : "Send to X4",
    "default_popup" : "src/popup/popup.html",
    "default_icon" : {
      "16" : "assets/icon16.png",
      "48" : "assets/icon48.png",
      "128" : "assets/icon128.png"
    }
  },
  "icons" : {
    "16" : "assets/icon16.png",
    "48" : "assets/icon48.png",
    "128" : "assets/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "send-to-x4-signed@xatpy.dev",
      "strict_min_version": "128.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "content_security_policy" : {
    "extension_pages": "script-src 'self'; object-src 'self'; connect-src http: https: ws: wss: * data: blob: filesystem:;"
  }
}