chore: add issue and pull request templates

[cxhello]

What type of PR is this?

• CI/CD

What does this PR do?

• Add issue templates for bug reports, feature requests, and questions
• Add pull request template to standardize PR descriptions
• Add template config with link to Nacos documentation

Template	Purpose
ISSUE_TEMPLATE/bug_report.md	Collect environment info, reproduction steps, and error logs
ISSUE_TEMPLATE/feature_request.md	Describe use case and proposed solution (V2/V3)
ISSUE_TEMPLATE/question.md	Usage questions with context
ISSUE_TEMPLATE/config.yml	Allow blank issues + link to Nacos docs
pull_request_template.md	Standardize PR type, description, related issues, and testing

Which issue(s) does this PR fix?

N/A

How has this been tested?

Verified templates render correctly on GitHub.

[Sunrisea]

Thanks for adding the templates! Overall LGTM, a few tweaks before merge:

1. Drop the V2 / V3 field. This repo only ships v2/ — no v3/ package or imports exist. Offering that choice will mislead reporters. Applies to bug_report.md, feature_request.md, question.md.

2. Refresh stale examples in bug_report.md. SDK Package Version: 2.0.5 → 3.2.0b1; Nacos Server Version: 2.4.0 → 3.0.3.

3. Add a Checklist to pull_request_template.md:

### Checklist
- [ ] Unit tests added/updated
- [ ] Documentation updated (if needed)
- [ ] No breaking changes (or described above)

4. Consider migrating to YAML Issue Forms (follow-up). The current .md + front-matter format is legacy. YAML forms (.yml) support required fields, dropdowns (Python / Nacos Server versions), and prerequisite checkboxes — much better UX. Can be a separate PR.

[cxhello]

@Sunrisea 改完了 再看看是否可以

[Sunrisea]

LGTM