WN: v10 RC1: Add OpenAPI Schema Generation Enhancements

[wadepickett]

Fixes #36078

Adds RC1 OpenAPI schema generation enhancements to the the What's New topic as an include.

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Internal previews

📄 File	🔗 Preview link
aspnetcore/release-notes/aspnetcore-10.0.md	What's new in ASP.NET Core in .NET 10

[Copilot]

Pull Request Overview

This PR adds documentation for OpenAPI schema generation enhancements in .NET 10 RC1. It addresses issue #36078 by creating a comprehensive overview of the new OpenAPI features and improvements.

Key changes:

• Creates a new include file documenting six OpenAPI schema generation improvements
• Integrates the new documentation into the main .NET 10 release notes
• Updates the documentation date to reflect the RC1 timeframe

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
aspnetcore/release-notes/aspnetcore-10/includes/openapi-schema-enhancements.md	New include file documenting OpenAPI schema generation enhancements including nullable types handling, schema reference resolution, property descriptions, XML comments support, HTTP method filtering, JSON Patch improvements, and invariant culture usage
aspnetcore/release-notes/aspnetcore-10.0.md	Updates the main release notes to include the new OpenAPI enhancements documentation and updates the modification date