DOC: Replace issue templates by issue forms

GitHub's issue forms are the next evolution of issue templates and allow for
showing an actual form with separate inputs when creating an issue. They ensure
that all the required fields are filled in and automatically format code parts
(e.g. haproxy -vv or the configuration) as actual code blocks, possibly with
syntax highlighting.

Co-authored-by: Maximilian Mader <max@bastelstu.be>
7 files changed