Sample code for working with .NET Entity Framework

There is a [sample project demonstrating how to use .NET EF Core with Dolt](https://github.com/dolthub/efcore-sample), but not one for Doltgres yet. We should create a similar sample project for Doltgres. This will be helpful for .NET customers and also a good check that another popular ORM works with Doltgres.

Start by reviewing the linked efcore-sample project and the Doltgres repository to understand the expected sample structure and connection setup. Create a comparable Doltgres sample for .NET Entity Framework Core, and verify that it demonstrates the ORM working with Doltgres for customers.

Written by the indexing model from the issue text.