Add support to placing project in root when using post-action AddProjectsToSolutionPostAction

[Tasteful]

When executing the dotnet sln .. add we have the ability to add the extra --in-root to allow the project to be placed in the root folder. In the template configuration there only exists possibility to set the --solution-folder but even if that is set to empty string the project is not placed in root.

[bekir-ozturk]

Hi @Tasteful, Thanks for the issue. ​This currently isn't in our top priority bucket, but we see the value in implementing this in the future. ​ We think this issue is an easy one for new contributors. If anyone is interested, please consider contributing by creating a PR.

[levimatheri]

@bekir-ozturk @vlada-shubina I'm interested in taking this up. I was trying to look for the source for the post action processor, I don't see it here https://github.com/dotnet/sdk/tree/main/src/Cli/Microsoft.TemplateEngine.Cli/PostActionProcessors.

[vlada-shubina]

@levimatheri this code was moved to sdk repo: https://github.com/dotnet/sdk/tree/main/src/Cli/dotnet/commands/dotnet-new/PostActions

Thank you for looking at this!

[levimatheri]

Thanks @vlada-shubina

[vlada-shubina]

Already done