Motivation / Problem

Few days ago GitHub released "Issue Forms" in beta. It is a new more friendly way to guide users through the issue templates. Read more about it here:
https://github.blog/changelog/2021-06-23-issues-forms-beta-for-public-repositories/

Description

Implemented the "Issue Forms" for OpenTTD. It is basically the same template as we had, just with a bit more guidance. Especially for crash, I put a lot more focus on uploading the zip-file with the crash-files.

https://github.com/TrueBrain/OpenTTD/issues/new?assignees=&labels=&template=bug.yaml&title=%5BBug%5D%3A+
https://github.com/TrueBrain/OpenTTD/issues/new?assignees=&labels=&template=crash.yaml&title=%5BCrash%5D%3A+

Limitations

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker