Fixing issue with losing unsafe keyword on using statement (#1417)

closes #1416

Author: belav

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/UsingDirectives.test

@@ -3,6 +3,7 @@ using A; // trailing
 // leading with space
 using // another trailing
 B;
+using unsafe NvapiQueryInterface = delegate* unmanaged[Cdecl]<uint, nint>;
 
 namespace Namespace
 {

Src/CSharpier/SyntaxPrinter/SyntaxNodePrinters/UsingDirective.cs

@@ -12,6 +12,7 @@ public static Doc Print(
             printExtraLines ? ExtraNewLines.Print(node) : Doc.Null,
             Token.PrintWithSuffix(node.GlobalKeyword, " ", context, skipLeadingTrivia: true),
             Token.PrintWithSuffix(node.UsingKeyword, " ", context, skipLeadingTrivia: true),
+            Token.PrintWithSuffix(node.UnsafeKeyword, " ", context, skipLeadingTrivia: true),
             Token.PrintWithSuffix(node.StaticKeyword, " ", context, skipLeadingTrivia: true),
             node.Alias == null ? Doc.Null : NameEquals.Print(node.Alias, context),
             Node.Print(node.NamespaceOrType, context),