Update version to 5.3.1 (#1082)

Directory.Build.props

@@ -7,7 +7,7 @@
     </PropertyGroup>
 
     <PropertyGroup>
-       <Version>5.3.0</Version>
+       <Version>5.3.1</Version>
    </PropertyGroup>
 
     <PropertyGroup>

README.md

@@ -11,7 +11,7 @@ MonoGame.Extended is a set of utilities (in the form of libraries/tools) to [Mon
 Code is distributed as NuGet packages in the form of libraries (`.dll` files). You can easily install the NuGet packages into your existing MonoGame project using the NuGet Package Manager UI in Visual Studio or by using the command line interface (CLI) in a terminal.
 
 ```sh
-dotnet add package MonoGame.Extended --version 5.0.2
+dotnet add package MonoGame.Extended --version 5.3.1
 ```
 
 ### Using the Content Pipeline Extensions