Create An Issue Template for Akka.persistence.linq2db

We should provide an issue template to make it easier for users to provide the right information to help them. Here's a draft I put together:

When Filing an issue, please provide as much of this information as possible:

- What Database you are using (e.g. "MS SQL Server 2014", or "PostgreSQL 8.3")
- Your version of Akka.NET
- Your version of Akka.Persistence.Linq2db
- Your version of Linq2Db installed (especially if it is different from what is bundled!)
- Whether you are on .NET Framework, Core, and which version of such.
- As much of your configuration as possible, **For security reasons, please do not include any passwords, and please do not use real server names.**

Start by reviewing the repository's existing issue-template conventions, if any, and compare them with the draft in this issue. Create the template so it requests the listed database, Akka.NET, Akka.Persistence.Linq2db, Linq2Db, platform, and configuration details while retaining the security warnings; done means users can select it when filing an issue.

Written by the indexing model from the issue text.