Add .slnx to default .editorconfig template

[lbussell]

.slnx files should match the same indentation settings as .csproj and other XML-based project files. This PR adds .slnx to the default .editorconfig template that's used by dotnet new editorconfig.

/cc @baronfel

[Copilot]

Pull Request Overview

This PR adds .slnx files to the default .editorconfig template to ensure consistent indentation settings across all XML-based project files. The change ensures that new solution files using the .slnx format follow the same 2-space indentation as other XML project files.

• Adds .slnx to the existing XML project files pattern in .editorconfig
• Removes trailing whitespace at the end of the file

[github-actions]

This PR is targeting main, which is now for .NET 11-facing work. If you intended to target .NET 10, either retarget this PR to release/10.0.1xx or make sure you backport the change to release/10.0.1xx after merging. See #50394 for more details.

[lbussell]

(force pushed to remove unnecessary whitespace diffs)

[baronfel]

@lbussell can you update the template test baselines for the editorconfig template?

[lbussell]

@lbussell can you update the template test baselines for the editorconfig template?

@baronfel is 55819bd what you were looking for?

[marcpopMSFT]

@baronfel should this be a candidate for GA or just 2xx?

[baronfel]

GA would be nice if possible - there was a whole discussion about the editorconfig on .NET Product Chat yesterday that we may want to quickly address.

EDIT: That conversation was about the GitHub-managed VisualStudio editorconfig, not ours, so we're clear to go ahead here.

[baronfel]

TBH, this feels so trivially correct and not-breakable to me that it could be tell-mode.

[lbussell]

Repo maintainers, feel free to merge when appropriate.

[baronfel]

I'll go ahead and merge to main - we can do a backport for 10 GA next!

[baronfel]

/backport to release/10.0.1xx

[github-actions]

Started backporting to release/10.0.1xx: https://github.com/dotnet/sdk/actions/runs/18176971262