publish only on release

Author: Filip Staffa

.github/workflows/dotnetcore.yml

@@ -45,5 +45,6 @@ jobs:
         run: dotnet-validate package local out/*.nupkg
 
       - name: Publish
+        if: github.event_name == 'release'
         run: |
           dotnet nuget push out/PostalCodes.${{ env.VERSION }}.nupkg -k ${{ secrets.NUGET_API_KEY }} -s https://api.nuget.org/v3/index.json