Work CI-CD

- NuGet package publish is now done against nuget.org.
- Remove private Azure feed from nuget.config.

NuGet.Config

@@ -2,6 +2,5 @@
 <configuration>
     <packageSources>
         <add key="NuGet" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
-        <add key="Azure Artifacts nanoFramework dev" value="https://pkgs.dev.azure.com/nanoframework/feed/_packaging/sandbox/nuget/v3/index.json" protocolVersion="3" />
     </packageSources>
 </configuration>

azure-pipelines.yml

@@ -261,17 +261,21 @@ jobs:
     condition: succeeded()
     displayName: Set build number
 
-  # push NuGet packages to Azure Artifacts feed (always happens except on PR builds)
+  # push NuGet packages to NuGet (always happens except on PR builds)
   - task: NuGetCommand@2
-    displayName: Push NuGet packages to Azure Artifacts
-    condition: and( succeeded(), eq(variables['System.PullRequest.PullRequestId'], '') )
+    displayName: Push NuGet packages to NuGet
+    condition: >-
+      and(
+        succeeded(),
+        eq(variables['System.PullRequest.PullRequestId'], '')
+      )
     continueOnError: true
     inputs:
       command: push
       nuGetFeedType: external
-      packagesToPush: '$(Build.ArtifactStagingDirectory)/*.nupkg'
-      publishFeedCredentials: 'AzureArtifacts'
       allowPackageConflicts: true
+      packagesToPush: '$(Build.ArtifactStagingDirectory)/*.nupkg'
+      publishFeedCredentials: 'NuGet-$(System.TeamProject)'
 
   # create or update GitHub release
   - task: GithubRelease@1