Update What's New for .NET 9 to elevate the "Optimize static web asset delivery" section to be a top-level section

[danroth27]

Description

The optimized handling of static web assets is one of the larger features in the .NET 9 release, so I'd like to elevate it to be a top-level section in the What's New doc instead of being a subsection under Miscellaneous.

Page URL

https://learn.microsoft.com/en-us/aspnet/core/release-notes/aspnetcore-9.0?view=aspnetcore-9.0

Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/release-notes/aspnetcore-9.0.md

Document ID

4e75ad25-2c3f-b28e-6a91-ac79a9c683b6

Article author

@Rick-Anderson

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Associated WorkItem - 340549