Add GitHub issue templates

## Goal
Add clear GitHub issue templates that help contributors report bugs and propose features.

## Suggested scope
- Add a bug-report template.
- Add a feature-request template.
- Ask for reproduction steps, expected behavior, actual behavior, and relevant environment details.
- Keep the templates concise and welcoming for first-time contributors.

## Acceptance criteria
- New issues can be opened through the available templates.
- Each template renders correctly on GitHub.
- The wording is written in clear English.

Start by inspecting the repository's GitHub configuration to find where issue templates belong. Add separate bug-report and feature-request templates covering the requested details, then open the new-issue flow on GitHub to verify both templates render correctly and use clear, welcoming English.

Written by the indexing model from the issue text.