// Important: return the modified config
    return config
  },
}
The webpack function is executed twice, once for the server and once for the client. This allows you to distinguish between client and server configuration using the isServer property.
The second argument to the webpack function is an object with the following properties:
buildId: String - The build id, used as a unique identifier between builds
dev: Boolean - Indicates if the compilation will be done in development
isServer: Boolean - It's true for server-side compilation, and false for client-side compilation
nextRuntime: String | undefined - The target runtime for server-side compilation; either "edge" or "nodejs", it's undefined for client-side compilation.
defaultLoaders: Object - Default loaders used internally by Next.js:
babel: Object - Default babel-loader configuration
Example usage of defaultLoaders.babel:
 // Example config for adding a loader that depends on babel-loader