MNT: Add issue and PR templates

[pllim]

This pull request adds templates for new issues and pull requests. For issues, they are separated into feature request, bug report, and question categories. Also see https://docs.github.com/en/free-pro-team@latest/github/building-a-strong-community/using-templates-to-encourage-useful-issues-and-pull-requests

[ejeschke]

Is there a way to try it out from the PR?

[pllim]

Unfortunately, I don't think so. But I have deployed similar templates elsewhere. So you can look at https://github.com/spacetelescope/synphot_refactor/issues/new/choose for examples of how the issue templates would work. As for PR template, you won't see it in action until you open a PR against that repo, but it basically pre-fill the body of the PR, so instead of blank, you get those words you see on the template.

[ejeschke]

@pllim, this looks reasonable to me. I think my only concern is that for some users this may set enough "friction" that they don't follow through with an issue ("ah, there's all these fields! I won't bother").

But then again perhaps this will make it easier for them by the prompts. In any case, we can adjust it later as needed.

[pllim]

Indeed, not everyone reads the template, but from the experience over at astropy, you might have maybe 50% success rate. 😉

[pllim]

I'll let you merge if you choose to accept the template. 😄