Add post-release script

[kosciCZ]

There could be a use case, when user might want to do something right after release, like trigger a docker hub build, or send an email to somewhere.

TBD:

• which from should the script be. Python? Bash?

[fridex]

There could be a use case, when user might want to do something right after release, like trigger a docker hub build, or send an email to somewhere.

JFYI, in thoth-station we are monitoring new releases on PyPI. If you would like to have some triggers, we already support OpenShift generic webhooks.

[TomasTomecek]

We don't consider this issue to be a prio.