[Copilot]

Summary

This PR makes the package consumable from Azure Functions isolated-worker apps targeting .NET 8 and .NET 9 without dropping .NET 10 support. It multi-targets the library and test project, and makes CI verify each supported TFM explicitly.

• Target frameworks

  • Library now targets net8.0;net9.0;net10.0
  • Test project now targets net8.0;net9.0;net10.0

• CI coverage

  • Replaced the single solution-level test invocation with explicit test runs for:
    • net8.0
    • net9.0
    • net10.0
  • Keeps framework support visible and enforced in CI

• Docs

  • Updated README and CONTRIBUTING to reflect package support for .NET 8/9/10
  • Kept repo-level SDK guidance aligned with the sample app still targeting .NET 10

<TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks>

Related issue

Linked automatically by the system.

Type of change

• Bug fix
• New feature
• Documentation
• Refactor / internal
• Build / CI

Checklist

• Targets the dev branch
• Added or updated tests for the change
• dotnet test --solution AzureExtensions.Functions.OpenApi.slnx -c Release passes locally
• Updated README/docs if public behavior changed
• Change is focused and free of unrelated churn

Notes for reviewers

• The sample app remains net10.0; only the published package and test project were broadened.
• CI now proves the supported package TFMs directly instead of relying on a single aggregate test command.

• Fixes [Feature]: Multi-target the package for .NET 8, .NET 9 and .NET 10 #12