add #nullable restore to decorator template to resolve compiler warning CS8669 (#57)

Author: marek-wolanowski-opennet

DecoratorGenerator.UnitTests/BirdDecorator.generated.cs

@@ -1,4 +1,5 @@
 // <auto-generated/>
+#nullable restore
 namespace SampleLibrary;
 
 public abstract class BirdDecorator : IBird

DecoratorGenerator.UnitTests/CatDecorator.generated.cs

@@ -1,4 +1,5 @@
 // <auto-generated/>
+#nullable restore
 namespace SampleLibrary;
 
 public abstract class CatDecorator : ICat

DecoratorGenerator.UnitTests/DynamoDBContextDecorator.generated.cs

@@ -1,4 +1,5 @@
 // <auto-generated/>
+#nullable restore
 namespace Amazon.DynamoDBv2.DataModel;
 
 public abstract class DynamoDBContextDecorator : IDynamoDBContext

DecoratorGenerator.UnitTests/LionPropertiesDecorator.generated.cs

@@ -1,4 +1,5 @@
 // <auto-generated/>
+#nullable restore
 namespace SampleLibrary;
 
 public abstract class LionPropertiesDecorator : ILionProperties

DecoratorGenerator.UnitTests/NestedDecorator.generated.cs

@@ -1,4 +1,5 @@
 // <auto-generated/>
+#nullable restore
 namespace SampleLibrary.Deep.Nesteds;
 
 public abstract class NestedDecorator : INested

DecoratorGenerator/OutputGenerator.cs

@@ -20,6 +20,7 @@ public static (string source, string className) GenerateOutputs(INamedTypeSymbol
 
             var source =
 $@"// <auto-generated/>
+#nullable restore
 namespace {type.ContainingNamespace.ToDisplayString()};
 
 public abstract class {className} : {@interface.Name}