Improve issue templates

[HonkingGoose]

What

Improve issue templates, migrate to Issue Forms, standardize forms.

Why

Make issue templates looks more like the ones we have over on the main Renovate repository.
Right now they're using an outdated format, and are harder to fill out than having a form.

How

I propose we move them to a Issue Form, and make them similar to the ones we use on the main Renovate repository.

What kind of issue forms do we need? I think we need at least these:

• Bug report form
• Feature request form
• Refactor form for other things like refactoring, docs proposals, and so on