Add checklists to issue templates & fix the formatting

[koibtw]

Type of Change

• [x] Documentation Update

Description

Added a checklist that includes:

• Checking for duplicate issues and discussions
• Checking the roadmap
• (for bug_report) Checking is the issue is present on both stable and dev branches

Fixed the formatting in feature_request.md to match bug_report.md.

Checklist

• [x] I have made corresponding changes to the documentation.
• [x] My changes generate no errors/warnings/merge conflicts.