Tweak logging.md (#1601)

docfx/logging.md

@@ -4,6 +4,8 @@ Logging
 SSH.NET uses the [Microsoft.Extensions.Logging](https://learn.microsoft.com/dotnet/core/extensions/logging) API to log diagnostic messages. In order to access the log messages of SSH.NET in your own application for diagnosis, register your own `ILoggerFactory` before using the SSH.NET APIs, for example:
 
 ```cs
+using Microsoft.Extensions.Logging;
+
 ILoggerFactory loggerFactory = LoggerFactory.Create(builder =>
 {
     builder.SetMinimumLevel(LogLevel.Debug);
@@ -11,5 +13,6 @@ ILoggerFactory loggerFactory = LoggerFactory.Create(builder =>
 });
 
 Renci.SshNet.SshNetLoggingConfiguration.InitializeLogging(loggerFactory);
+```
 
 All messages by SSH.NET are logged under the `Renci.SshNet` category.