Use .NET 5 in release pipeline

Former-commit-id: 04f78b01e5

.github/workflows/release.yml

@@ -9,6 +9,10 @@ jobs:
     steps:
     - name: Checkout
       uses: actions/checkout@v1
+    - name: Prepare .NET
+      uses: actions/setup-dotnet@v1
+      with:
+        dotnet-version: '5.0.x'
     - name: Build solution
       run: dotnet build --output build -c Release
     - name: Publish NuGet package