docs: refactor issue templates and adjust base readme

[Ryun1]

List of changes

• Changed and improved the new feature issue template
• Added workflow to add labels to new feature issues
• Changed and improved the bug report template
• Added workflow to add labels to new bug report issues
• Tweak base readme

Checklist

• related issue
• My changes generate no new warnings
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the changelog
• I have added tests that prove my fix is effective or that my feature works