userdiff: add support for C# record types

Records are added in C# 9

Code example :

    public record Person(string FirstName, string LastName);

For more information, see:
* https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-9

Signed-off-by: Julian Verdurmen <julian.verdurmen@outlook.com>
Reviewed-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

userdiff.c

@@ -65,7 +65,7 @@ PATTERNS("csharp",
 	 /* Properties */
 	 "^[ \t]*(((static|public|internal|private|protected|new|virtual|sealed|override|unsafe)[ \t]+)*[][<>@.~_[:alnum:]]+[ \t]+[@._[:alnum:]]+)[ \t]*$\n"
 	 /* Type definitions */
-	 "^[ \t]*(((static|public|internal|private|protected|new|unsafe|sealed|abstract|partial)[ \t]+)*(class|enum|interface|struct)[ \t]+.*)$\n"
+	 "^[ \t]*(((static|public|internal|private|protected|new|unsafe|sealed|abstract|partial)[ \t]+)*(class|enum|interface|struct|record)[ \t]+.*)$\n"
 	 /* Namespace */
 	 "^[ \t]*(namespace[ \t]+.*)$",
 	 /* -- */