Update PublishNuget.yml

Added dotnet 7.0

Author: pjoiner

.github/workflows/PublishNuget.yml

@@ -14,6 +14,11 @@ jobs:
 
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
+      - name: Setup dotnet
+        uses: actions/setup-dotnet@v3
+        with:
+           dotnet-version: 7.0.x
+           
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
       - uses: actions/checkout@v3