Add .NET 10.0 target framework support to all projects and CI workflows

[Copilot]

This PR adds .NET 10.0 target framework support across all projects in the repository and updates the CI/CD pipeline to build and test against .NET 10.0.

Changes

Project Files

Updated all 5 project files to target both .NET 8.0 and .NET 10.0:

• OpenXmlToHtml/OpenXmlToHtml.csproj - Core library
• OpenXmlToHtmlCli/OpenXmlToHtmlCli.csproj - CLI tool
• OpenXmlToHtmlOpenApi/OpenXmlToHtmlOpenApi.csproj - Web API
• OpenXmlToHtmlTests/OpenXmlToHtmlTests.csproj - Unit tests
• OpenXmlToHtmlOpenApiTests/OpenXmlToHtmlOpenApiTests.csproj - Integration tests

Projects that previously used singular TargetFramework have been updated to use plural TargetFrameworks with both net8.0;net10.0 targets.

GitHub Actions Workflow

Updated .github/workflows/dotnet.yml to install both .NET 8.0.x and 10.0.x SDKs in all three jobs:

• build - Runs on Ubuntu and Windows, building and testing both frameworks
• deployRelease - Deployment job for the release branch
• deployTest - Deployment job for the main branch

The workflow now uses the multi-line syntax for dotnet-version:

dotnet-version: |
  8.0.x
  10.0.x

Benefits

• Future-proof: Once .NET 10.0 is officially released, projects will automatically build for both frameworks
• Backward compatible: Maintains full .NET 8.0 support
• Comprehensive testing: CI pipeline will validate compatibility with both .NET 8.0 and 10.0
• Early adoption: Ready to leverage .NET 10.0 features and improvements as soon as it's available

Notes

The changes are ready for the .NET 10.0 release. The CI builds will succeed on .NET 8.0 targets immediately, and will automatically include .NET 10.0 builds once the SDK is available in GitHub Actions runners.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://storage.googleapis.com/chrome-for-testing-public/138.0.7204.92/linux64/chrome-linux64.zip
  • Triggering command: /usr/share/dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/OpenXmlToHtml/OpenXmlToHtml/OpenXmlToHtmlTests/bin/Release/net8.0/OpenXmlToHtmlTests.runtimeconfig.json --depsfile /home/REDACTED/work/OpenXmlToHtml/OpenXmlToHtml/OpenXmlToHtmlTests/bin/Release/net8.0/OpenXmlToHtmlTests.deps.json /home/REDACTED/work/OpenXmlToHtml/OpenXmlToHtml/OpenXmlToHtmlTests/bin/Release/net8.0/testhost.dll --port 43795 --endpoint 127.0.0.1:043795 --role client --parentprocessid 3740 --telemetryoptedin false (http block)
  • Triggering command: /usr/share/dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/OpenXmlToHtml/OpenXmlToHtml/OpenXmlToHtmlOpenApiTests/bin/Release/net8.0/OpenXmlToHtmlOpenApiTests.runtimeconfig.json --depsfile /home/REDACTED/work/OpenXmlToHtml/OpenXmlToHtml/OpenXmlToHtmlOpenApiTests/bin/Release/net8.0/OpenXmlToHtmlOpenApiTests.deps.json /home/REDACTED/work/OpenXmlToHtml/OpenXmlToHtml/OpenXmlToHtmlOpenApiTests/bin/Release/net8.0/testhost.dll --port 38469 --endpoint 127.0.0.1:038469 --role client --parentprocessid 3733 --telemetryoptedin false (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Update all project files in the repository to add net10.0 to the TargetFrameworks or TargetFramework property, if not already present. Also, update any GitHub Actions workflow files (e.g., .github/workflows/build.yml) to include .NET SDK version 10.0.x in the build matrix or setup-dotnet steps, ensuring CI builds and tests for .NET 10 as well. Make these updates for all mainline projects and the primary CI build workflow.

This pull request was created as a result of the following prompt from Copilot chat.

Update all project files in the repository to add net10.0 to the TargetFrameworks or TargetFramework property, if not already present. Also, update any GitHub Actions workflow files (e.g., .github/workflows/build.yml) to include .NET SDK version 10.0.x in the build matrix or setup-dotnet steps, ensuring CI builds and tests for .NET 10 as well. Make these updates for all mainline projects and the primary CI build workflow.

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[github-actions]

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I have read the CLA Document and I hereby sign the CLA

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[github-actions]

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