docs: update readme.md for 13.1.0 release

Signed-off-by: Kenny Pflug <kenny.pflug@live.de>

Author: feO2x

README.md

@@ -2,8 +2,8 @@
 **A lightweight .NET library for expressive Guard Clauses.** 
 
 [![License](https://img.shields.io/badge/License-MIT-green.svg?style=for-the-badge)](https://github.com/feO2x/Light.GuardClauses/blob/master/LICENSE)
-[![NuGet](https://img.shields.io/badge/NuGet-13.0.0-blue.svg?style=for-the-badge)](https://www.nuget.org/packages/Light.GuardClauses/)
-[![Source Code](https://img.shields.io/badge/Source%20Code-13.0.0-blue.svg?style=for-the-badge)](https://github.com/feO2x/Light.GuardClauses/blob/master/Light.GuardClauses.SingleFile.cs)
+[![NuGet](https://img.shields.io/badge/NuGet-13.1.0-blue.svg?style=for-the-badge)](https://www.nuget.org/packages/Light.GuardClauses/)
+[![Source Code](https://img.shields.io/badge/Source%20Code-13.1.0-blue.svg?style=for-the-badge)](https://github.com/feO2x/Light.GuardClauses/blob/master/Light.GuardClauses.SingleFile.cs)
 [![Documentation](https://img.shields.io/badge/Docs-Wiki-yellowgreen.svg?style=for-the-badge)](https://github.com/feO2x/Light.GuardClauses/wiki)
 [![Documentation](https://img.shields.io/badge/Docs-Changelog-yellowgreen.svg?style=for-the-badge)](https://github.com/feO2x/Light.GuardClauses/releases)
 
@@ -94,7 +94,7 @@ Every assertion is well-documented - explore them using IntelliSense or check ou
 
 ## Light.GuardClauses is optimized
 
-Since version 4, **Light.GuardClauses** is optimized for performance (measured in .NET 4.8 and .NET 6). With the incredible help of [@redknightlois](https://github.com/redknightlois) and the awesome tool [BenchmarkDotNet](https://github.com/dotnet/BenchmarkDotNet), most assertions are as fast as your imperative code would be.
+Since version 4, **Light.GuardClauses** is optimized for performance (measured in .NET 4.8 and .NET 8). With the incredible help of [@redknightlois](https://github.com/redknightlois) and the awesome tool [BenchmarkDotNet](https://github.com/dotnet/BenchmarkDotNet), most assertions are as fast as your imperative code would be.
 
 **Light.GuardClauses** has support for [.NET analyzers / FxCopAnalyzers](https://docs.microsoft.com/en-us/dotnet/fundamentals/code-analysis/overview) with the `ValidatedNotNullAttribute` and the `NotNullAttribute`. Analyzers will know when an assertion validated that a parameters is not null and consequently, CA1062 will not be raised.
 
@@ -116,7 +116,7 @@ Light.GuardClauses is available as a [NuGet package](https://www.nuget.org/packa
 
 - **dotnet CLI**: `dotnet add package Light.GuardClauses`
 - **Visual Studio Package Manager Console**: `Install-Package Light.GuardClauses`
-- **Package Reference in csproj**: `<PackageReference Include="Light.GuardClauses" Version="13.0.0" />`
+- **Package Reference in csproj**: `<PackageReference Include="Light.GuardClauses" Version="13.1.0" />`
 
 Also, you can incorporate Light.GuardClauses as a **single source file** where the API is changed to `internal`. This is especially interesting for framework / library developers that do not want to have a dependency on the Light.GuardClauses DLL. You can grab the default .NET Standard 2.0 version in [Light.GuardClauses.SingleFile.cs](https://github.com/feO2x/Light.GuardClauses/blob/master/Light.GuardClauses.SingleFile.cs) or you can use the [Light.GuardClauses.SourceCodeTransformation](https://github.com/feO2x/Light.GuardClauses/tree/master/Code/Light.GuardClauses.SourceCodeTransformation) project to create your custom file. You can learn more about it [here](https://github.com/feO2x/Light.GuardClauses/wiki/Including-Light.GuardClauses-as-source-code).