Add Target Frameworks .net6.0 .net7.0 to MatrixDotNet.csproj

[toor1245]

Update TargetFrameworks in MatrixDotNet.csproj to:

<TargetFrameworks>net7.0;net6.0;net5.0;netcoreapp3.1;netstandard2.1</TargetFrameworks>

Also, in .net7.0 BinaryFormatter.Serialize and BinaryFormatter.Deserialize methods reports as error.
So need to add [Obsolete("Obsolete")] attribute to BinaryOpenAsync and BinarySaveAsync in Extensions/Template.cs