Implemented initial minimal support for native Excel add-ins

[Sergey-Vlasov]

Running MasterBuild\MasterBuild.cmd produces Package\nupkg\ExcelDna.AddIn.NativeAOT.0.1.0.nupkg.

Publishing the following C# project produces native 64-bit MyAddin.xll Excel add-in.

MyAddin.csproj:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net8.0-windows</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>

    <RuntimeIdentifier>win-x64</RuntimeIdentifier>
    <PublishAOT>true</PublishAOT>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="ExcelDna.AddIn.NativeAOT" Version="0.1.0" />
  </ItemGroup>

</Project>

Functions.cs:

using ExcelDna.Integration;

namespace MyAddin
{
    public class Functions
    {
        [ExcelFunction]
        public static string MyHello(string name)
        {
            return $"Hello {name}!";
        }

        [ExcelFunction]
        public static int MySum(int i1, int i2)
        {
            return i1 + i2;
        }
    }
}