Backport: appveyor.yml: Add inline deployment on tag push

Automate the deployment from appveyor.

We want to publish all artifacts as a new draft prelease on tag push only.

For reference see https://www.appveyor.com/docs/deployment/github/ and https://www.appveyor.com/docs/appveyor-yml/.

I have created a new github machine user named cppTango-bot for that. And also a personal access token which was encrypted on the appveyor site.