Merge pull request #1330 from bender2k14/#1328_syntatically_optional_…

…IFormatProvider

made formatProvider optional in the constructor of MessageTemplateTextFormatter

src/Serilog/Formatting/Display/MessageTemplateTextFormatter.cs

@@ -41,7 +41,7 @@ public class MessageTemplateTextFormatter : ITextFormatter
         /// <param name="outputTemplate">A message template describing the
         /// output messages.</param>
         /// <param name="formatProvider">Supplies culture-specific formatting information, or null.</param>
-        public MessageTemplateTextFormatter(string outputTemplate, IFormatProvider formatProvider)
+        public MessageTemplateTextFormatter(string outputTemplate, IFormatProvider formatProvider = null)
         {
             if (outputTemplate == null) throw new ArgumentNullException(nameof(outputTemplate));
             _outputTemplate = new MessageTemplateParser().Parse(outputTemplate);