Add issue templates

[BHChen24]

Goal

Add issue templates to make it easier for contributors to report bugs and request features.

Why

• Makes it easier for contributors
• Reduces back-and-forth clarification
• Helps maintainers triage issues faster

I can try to add these two templates to .github/ISSUE_TEMPLATE. Just need you to adjust some project-specific fields, like environment setup, dependencies, etc.
Let me know if you'd like me to proceed!