feat: add GitHub issue form templates
4 YAML form templates for structured feedback from the landing site FAB:
- bug_report.yml: page URL, browser, OS, steps, expected vs actual (update of existing)
- content_suggestion.yml: type, section, description, references
- quiz_error.yml: question ID, category, error type, suggested fix
- general_feedback.yml: type (UX/content/a11y/perf), message, page URL
- config.yml: blank_issues_enabled + Discussions link
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
4c42151151