feat: prepare SourceCodeTransformation project for v12.0 release

Signed-off-by: Kenny Pflug <[email protected]>

Author: feO2x

Code/Light.GuardClauses.Source/Light.GuardClauses.Source.csproj

@@ -1,8 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFrameworks>netstandard2.0</TargetFrameworks>
-        <LangVersion>10.0</LangVersion>
+        <TargetFramework>netstandard2.0</TargetFramework>
+        <LangVersion>12.0</LangVersion>
         <Authors>Kenny Pflug</Authors>
         <Company>Kenny Pflug</Company>
         <Copyright>Copyright © Kenny Pflug 2016 - 2023</Copyright>

Code/Light.GuardClauses.SourceCodeTransformation/SourceFileMerger.cs

@@ -34,7 +34,7 @@ public static void CreateSingleSourceFile(SourceFileMergeOptions options)
                      .AppendLine($@"License information for Light.GuardClauses
 
 The MIT License (MIT)
-Copyright (c) 2016, 2023 Kenny Pflug mailto:[email protected]
+Copyright (c) 2016, 2024 Kenny Pflug mailto:[email protected]
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the ""Software""), to deal
@@ -69,6 +69,7 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 using System.Text.RegularExpressions;
 {(options.IncludeJetBrainsAnnotationsUsing ? "using JetBrains.Annotations;" + Environment.NewLine : string.Empty)}using {options.BaseNamespace}.Exceptions;
 using {options.BaseNamespace}.FrameworkExtensions;
+{(options.IncludeJetBrainsAnnotationsUsing ? "using NotNullAttribute = System.Diagnostics.CodeAnalysis.NotNullAttribute;" : "")}
 
 #nullable enable annotations