Implement issue templates

[florisvdh]

Fixes #180.

This should help users to analyze and report their problems properly, enabling developers to proceed efficiently. Setup is based on the experience with several issues in the past, and was somehow inspired by how QGIS deals with this. Different issue categories lead to a different set of questions asked.

The result has been pushed to the main branch of my fork; so you can try out at https://github.com/florisvdh/qgisprocess/issues/new/choose (screenshot below). Feel free to post some dummy issues there (posting issues in my fork will be disabled later).

Developer community of the {qgisprocess} package: if you're in need to add a simple housekeeping issue, e.g. a task list for yourself, use the 'feature request' as it has the simplest form and no extra requirements. After posting, you can still edit as a normal issue.

Automated issue labelling is not enabled yet. We can consider this later on, after gathering more experience.

[paleolimbot]

No issues (pun slightly intended) from me...I wonder if this level of complexity will end up being helpful but it's definitely worth a shot!

[florisvdh]

Thanks for having a look Dewey.