Fix printing description on schema (#310)

Author: sungam3r

src/Directory.Build.props

@@ -1,7 +1,7 @@
 <Project>
 
   <PropertyGroup>
-    <VersionPrefix>8.0.0-preview</VersionPrefix>
+    <VersionPrefix>9.0.1-preview</VersionPrefix>
     <LangVersion>latest</LangVersion>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <NoWarn>$(NoWarn);CA1707</NoWarn>

src/GraphQLParser.Tests/Visitors/SDLPrinterFromParsedTextTests.cs

@@ -641,6 +641,19 @@ query q(
 $a: Int) {
   x
 }
+""")]
+    [InlineData(49,
+"""
+"description"
+schema {
+  query: Query
+}
+""",
+"""
+"description"
+schema {
+  query: Query
+}
 """)]
     public async Task SDLPrinter_Should_Print_Document(
         int number,

src/GraphQLParser/Visitors/SDLPrinter.cs

@@ -607,7 +607,7 @@ protected override async ValueTask VisitSchemaDefinitionAsync(GraphQLSchemaDefin
     {
         await VisitAsync(schemaDefinition.Comments, context).ConfigureAwait(false);
         await VisitAsync(schemaDefinition.Description, context).ConfigureAwait(false);
-        await context.WriteAsync("schema").ConfigureAwait(false);
+        await VisitAsync(LiteralNode.Wrap("schema"), context).ConfigureAwait(false);
         await VisitAsync(schemaDefinition.Directives, context).ConfigureAwait(false);
 
         //bool freshLine = schemaDefinition.Comments != null && Options.PrintComments; always false