appveyor.yml: Add inline deployment on tag push

[t-b]

Automate the deployment from appveyor.

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

I've published 9.3.4-rc1 from an environment in appveyor. This is an alternative solution to the inline deployment method.

For playing around I've used an OAuth token from my user. But we can not merge it as it is as using a token from a human user account is unsafe. This OAuth token allows read/write access to all repositories.

I propose to create a machine user which has only access to the cppTango repo and generate an OAuth token for her and use that here. See https://developer.github.com/v3/guides/managing-deploy-keys/#machine-users and https://help.github.com/en/github/authenticating-to-github/creating-a-personal-access-token-for-the-command-line?query=machine%20user.

Close #602.

[bourtemb]

I propose to create a machine user which has only access to the cppTango repo and generate an OAuth token for her and use that here.

Sounds good to me.

[NexeyaSGara]

Big yes :)
I didn't had the time to study the automatic deployment so I'm ok with that and the machine user

[t-b]

Updated. @bourtemb Could you grant the new machine user https://github.com/cppTango-bot access to the cppTango repo (and only to that, not to the full orga).

I've already created a personal access token for her.

[bourtemb]

Updated. @bourtemb Could you grant the new machine user https://github.com/cppTango-bot access to the cppTango repo (and only to that, not to the full orga).

@t-b , invitation sent to cppTango-bot.
Please tell me if the permissions are not correct.

[cppTango-bot]

@bourtemb Thanks. Ready to merge I guess.

[bourtemb]

Looks good to me. I Tried it on my fork and seems to work as expected.
Thanks @t-b , this will simplify our life when preparing a release.
We need to do the same in the 9.3-backports branch to get it for the 9.3.4 release.

[t-b]

@bourtemb Can you bend the rules and merge with just one approval?