This commit adds a new `Question.md` issue template that aims to prevent
users asking questions within the issue tracker, because the other two
templates do not fit "question", thus leading to people not seeing that
the issue tracker is not for questions.
This template inspired by TypeScript's Question template at:
https://github.com/microsoft/TypeScript/blob/master/.github/ISSUE_TEMPLATE/Question.md
Tim Duesterhus