chore: add issue templates and improve PR template

[miyoungc]

Summary

Add structured issue templates for bug reports, feature requests, and documentation issues. Enhance the PR template with contribution checklists aligned to the project's CONTRIBUTING.md guidelines.

Changes

• Add bug report issue template with required reproduction steps, environment details, and a reproducibility checklist.
• Add documentation issue template with affected page field, issue type dropdown, and optional suggested fix.
• Enhance feature request template to require a problem statement, proposed design, and a "not a wish list" gate.
• Add config.yml to disable blank issues and redirect security reports to SECURITY.md.
• Improve PR template with a "Type of Change" selector, separate checklists for code and doc changes, and a reference to the update-docs agent skill.

Type of Change

• Code change for a new feature, bug fix, or refactor.
• Code change with doc updates.
• Doc only. Prose changes without code sample modifications.
• Doc only. Includes code sample changes.

Testing

• make check passes.
• npm test passes.
• make docs builds without warnings. (for doc-only changes)

Checklist

General

• I have read and followed the contributing guide.
• I have read and followed the style guide. (for doc-only changes)

Doc Changes

• Follows the style guide.
• New pages include SPDX license header and frontmatter, if creating a new page.
• Cross-references and links verified.

[coderabbitai]

📝 Walkthrough

Walkthrough

GitHub issue and pull request templates were added and updated to standardize bug reports, feature requests, documentation issues, and PR processes. New configuration disables blank issues and directs security reports to a dedicated process.

Changes

Cohort / File(s)	Summary
GitHub Issue Templates .github/ISSUE_TEMPLATE/bug_report.yml, .github/ISSUE_TEMPLATE/doc_issue.yml, .github/ISSUE_TEMPLATE/feature_request.yml	New and updated issue form templates collecting structured information for bug reports (reproduction steps, environment), documentation issues (problem type, affected page), and feature requests (problem statement, proposed design, alternatives).
Template Configuration .github/ISSUE_TEMPLATE/config.yml	New configuration file disabling blank issues and routing security vulnerability reports to the SECURITY.md disclosure process.
Pull Request Template .github/PULL_REQUEST_TEMPLATE.md	Restructured PR checklist sections with added requirements to read contributing and style guides, improved punctuation and wording consistency across code and documentation change categories.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 Templates now tidied, with forms crystal clear,
Issue and PR workflows structured here,
Security reports find their proper way,
Organization blooms with each git day! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'chore: add issue templates and improve PR template' directly and accurately summarizes the main changes: adding issue templates and improving the PR template.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch add-issue-template

📝 Coding Plan

• Generate coding plan for human review comments

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_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[wscurran]

Looks good. Label "status: triage" will trigger view of all new bugs/prs to go into daily triage.