Update publishnuget.md with new docs

Added detailed documentation in `publishnuget.md` for GitHub Actions, focusing on the publishing process for NuGet packages. This includes a new section on Azure DevOps publishing, detailing the use of a Personal Access Token (PAT) for package publishing, its configuration in GitHub Actions secrets, and its validity period. Additionally, introduced a section on publishing to NuGet, providing relevant links for both Azure DevOps feeds and the NuGet server for *CNinnovation.Codebreaker.ViewModels*.

Author: christiannagel

publishnuget.md

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+# GitHub Actions
+
+## Publish to Azure DevOps
+
+[Azure DevOps feed for daily builds](https://pkgs.dev.azure.com/cnilearn/codebreakerpackages/_packaging/codebreaker/nuget/v3/index.json)
+
+Daily build version of NuGet packages (*CNinnovation.Codebreaker.ViewModels*) are published to Azure DevOps with every merge to the main branch.
+
+For publishing, an Azure DevOps PAT is required.
+Permissions: Packaging, Read & Write
+
+The PAT is configured with the environment *DevOpsArtifacts" actions secret *DEVOPS_ARTIFACT_PAT*.
+
+Valid until 2025/01/12
+
+## Publish to NuGet
+
+Preview and release versions are published to the NuGet server.
+
+[CNInnovation.Codebreaker.ViewModels](https://www.nuget.org/packages/CNInnovation.Codebreaker.ViewModels/)