Decide on issue templates

[asl]

We might want to specify some issue templates to help automating some tasks, e.g.:

• Backports for release
• Crash dumps (with automatic check whether reproducer is attached)
• ...

Note we can use YAML forms instead of markdown templates: https://github.blog/changelog/2021-06-23-issues-forms-beta-for-public-repositories/

[asl]

Tagging @tstellar for some ideas wrt release-related issue handing