Problem: no guide for user when creating new issue

Solution: add a simple issue template

see example at bigchaindb repo but keep it really really simple.
The purpose is to fulfil the community checklist on GitHub

Review the issue-template example in the BigchainDB repository and the GitHub community checklist referenced in the issue. Add a simple issue template for this repository, keeping it minimal and aligned with the checklist; done means users receive that guidance when creating an issue.

Written by the indexing model from the issue text.