Enable issue templates

[andregasser]

Activate issue templates for bugs and features.

[bocops]

I've seen UI to select one or another issue type in other GitHub projects, but never implemented something like this myself in a project - I assume these would be presented in such UI and can be automated somehow?

[andregasser]

By activating these two issue templates, the user must choose whether he wants to open a bug or a new feature. Tensorflow for example uses several issue templates to help the user file a new issue.

Here you can see it in action:
https://github.com/tensorflow/tensorflow/issues

I think we could start small and work with these two templates and modify them if needed.

I eventually need to tweak it further after this PR is merged (dependes on how these templates are presented).

[andregasser]

Change of plans: I will prepare issue templates in a separate github repo, so we do not pollute our commit history here.
Converted this PR to a draft. Will re-enable it once we have agreed on a set of templates 😀

[McPringle]

I would suggest to start with the default templates provided by GitHub. They can be added to the repository automatically and can tweaked later, if necessary. Just go to the settings page and enable them. I suggest to add all three (bug, feature, and blank) templates. Needs maybe one minute of work. 😉

Link (works only for repo admins): https://github.com/andregasser/bigbone/issues/templates/edit