feat(actions): add nuget trusted publishing

[micheloliveira-com]

Fixes #735

Motivation

As described in the official announcement, the new Trusted Publishing feature greatly enhances package publishing security on NuGet.org.

We successfully tested this approach with our own NuGet library:

• GitHub Actions run example
• Corresponding commit

Required changes in this repository

Recommendation followed from announcement:
For security, always use a GitHub secret like ${{ secrets.NUGET_USER }} for your NuGet.org username (profile name), not your email address.

• Add secrets.NUGET_USER to this repository, using the NuGet.org username (profile name) of the package owner ( Microsoft.Toolkit in this case).
• The old secrets.NUGET_PACKAGE_PUSH_TOKEN secret can be removed from this repository and also from the NuGet.org account if it was only used here.

One-time configuration on NuGet.org

According to the documentation:

1. Sign in to NuGet.org.
2. Open your user menu (top-right) → Trusted Publishing (next to “API Keys”).
3. Create a policy:
   • Package owner: you or your organization (e.g. Microsoft.Toolkit).
   • Repository owner: your GitHub org/user (e.g. CommunityToolkit).
   • Repository name: repository name (e.g. Windows).
   • Workflow file: the YAML file under .github/workflows/ (e.g. build.yml).
   • Environment (optional): specify if your workflow uses GitHub Actions environments.

This setup eliminates the need for long-lived API keys and improves the overall security of the publishing process.

PR Type

What kind of change does this PR introduce?

Nuget Trusted Publishing in .github/workflows/build.yml.

What is the current behavior?

What is the new behavior?

PR Checklist

Please check if your PR fulfills the following requirements:

• Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• Based off latest main branch of toolkit
• Tested code with current supported SDKs
• New component
  • Documentation has been added
  • Sample in sample app has been added
  • Analyzers are passing for documentation and samples
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• Tests for the changes have been added (if applicable)
• Header has been added to all new source files
• Contains NO breaking changes

Other information