Include argument name when throwing ArgumentException

Author: nblumhardt

src/Serilog.Sinks.File/FileLoggerConfigurationExtensions.cs

@@ -183,7 +183,7 @@ static LoggerConfiguration ConfigureFile(
 #endif
 
                 if (buffered)
-                    throw new ArgumentException("Buffered writes are not available when file sharing is enabled.");
+                    throw new ArgumentException("Buffered writes are not available when file sharing is enabled.", nameof(buffered));
             }
 
             ILogEventSink sink;