Update Roslyn version support for Visual Studio 2026

[ToddGrun]

Note: I am an internal contributor, but neither the private repo link nor the link to join the MicrosoftDocs GitHub organization were working.

[prmerger-automator]

@ToddGrun : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

[learn-build-service-prod]

Learn Build status updates of commit 75e2672:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/extensibility/roslyn-version-support.md	✅Succeeded

For more details, please refer to the build report.

[ktoliver]

@tinaschrepfer

Can you review the proposed changes?

IMPORTANT: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
@MicrosoftDocs/public-repo-pr-review-team

[ToddGrun]

@tinaschrepfer -- Is there anything else needed from my side for this?

[ToddGrun]

@tinaschrepfer -- PTAL

[Copilot]

Pull request overview

This PR updates the Roslyn version support documentation to include Visual Studio 2026 preview/upcoming release information. The change adds a mapping for Roslyn package version 5.0.0 to the documentation table.

• Adds support information for Roslyn package version 5.0.0 with Visual Studio 2026 version 18.0

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