build: add dotnet setup before nuke push

Author: loekensgard

.github/workflows/Publish.yml

@@ -36,6 +36,10 @@ jobs:
             .nuke/temp
             ~/.nuget/packages
           key: ${{ runner.os }}-${{ hashFiles('**/global.json', '**/*.csproj', '**/Directory.Packages.props') }}
+      - name: Setup dotnet
+        uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: '8.0.x'
       - name: 'Run: Push'
         run: ./build.cmd Push
         env: