GitHub Issues Template for Bugs

[ChristopherA]

We should create a GitHub issues template with best practices of reporting for reporting bugs here, as well as a warning avoid to sharing screenshots with key material, and if they need to do that have the contact us privately.

@gorazdko could you look around for a first pass on what other repos use as a bug reporting template, set it up here, and give it to @shannona to edit and for possible use in other repos.