Fix mixed path separators in NuGet push on Windows (#393)

Use PowerShell with $env:GITHUB_WORKSPACE and backslash separators
for dotnet nuget push. Use relative paths for GitHub Release action
which handles glob expansion internally.

Author: Aaronontheweb

.github/workflows/release.yaml

@@ -70,17 +70,18 @@ jobs:
             -v Information
 
       - name: Push to NuGet.org
-        run: >
-          dotnet nuget push "${{ github.workspace }}/bin/nuget/*.nupkg"
-          --api-key ${{ secrets.NUGET_API_KEY }}
-          --source https://api.nuget.org/v3/index.json
-          --skip-duplicate
+        shell: pwsh
+        run: |
+          dotnet nuget push "$env:GITHUB_WORKSPACE\bin\nuget\*.nupkg" `
+            --api-key ${{ secrets.NUGET_API_KEY }} `
+            --source https://api.nuget.org/v3/index.json `
+            --skip-duplicate
 
       - name: Create GitHub Release
         uses: softprops/action-gh-release@v2
         with:
           name: "TurboMqtt v${{ steps.version.outputs.version }}"
           body_path: RELEASE_NOTES.md
           files: |
-            ${{ github.workspace }}/bin/nuget/*.nupkg
-            ${{ github.workspace }}/bin/nuget/*.snupkg
+            bin/nuget/*.nupkg
+            bin/nuget/*.snupkg