Update pack and publish to MyGet workflow (#3589)

.github/workflows/publish-packages-1.0.yml

@@ -32,6 +32,11 @@ jobs:
         fetch-depth: 0 # fetching all
         ref: ${{ matrix.branches }}
 
+    - uses: actions/setup-dotnet@v2
+      with:
+        dotnet-version: '7.0.x'
+        include-prerelease: true
+
     - name: Install dependencies
       run: dotnet restore