suggesting a pull-request-template. #3018

Intended Change

There is no guided process for writing PRs. But there should be. Therefore: Suggesting this template here.

Reason for the pull request

improving git/github maintenance workflow.

Touched elements

adding file to .github.

Information for the reviewer

I tested that a file in this place should in the future appear as pull-request template on an empty repo of my own. I assume it will work here to.