docs: add CONTRIBUTING.md and GitHub issue/PR templates

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: Report a problem with macapptree
+labels: bug
+---
+
+## Description
+
+A clear description of the bug.
+
+## Environment
+
+- macOS version:
+- Python version:
+- macapptree version:
+- Installation method (pip / source):
+
+## Accessibility permission granted?
+
+- [ ] Yes — terminal / Python has Accessibility access in System Settings
+
+## Steps to reproduce
+
+```python
+# Minimal example that triggers the bug
+```
+
+## Expected behavior
+
+What you expected to happen.
+
+## Actual behavior
+
+What actually happened. Include any error messages or stack traces.
+
+## Additional context
+
+Any other relevant information (app being captured, window state, etc.).

.github/ISSUE_TEMPLATE/feature_request.md

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+---
+name: Feature request
+about: Suggest an improvement or new capability
+labels: enhancement
+---
+
+## Summary
+
+A one-line description of the feature.
+
+## Motivation
+
+Why is this useful? What problem does it solve?
+
+## Proposed API / behavior
+
+If applicable, show what the interface would look like:
+
+```python
+# Example usage
+```
+
+## Alternatives considered
+
+Other approaches you thought about and why you prefer this one.
+
+## Additional context
+
+Links, screenshots, related issues, or anything else relevant.

.github/PULL_REQUEST_TEMPLATE.md

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+## Summary
+
+Describe what this PR does and why.
+
+## Changes
+
+- 
+- 
+
+## Type of change
+
+- [ ] Bug fix
+- [ ] New feature
+- [ ] Refactor / cleanup
+- [ ] Documentation
+- [ ] Other:
+
+## Testing
+
+Describe how you tested the change. Include the app bundle IDs you used, macOS version, and any edge cases exercised.
+
+## Checklist
+
+- [ ] Tested on macOS with Accessibility permission granted
+- [ ] No hardcoded paths or bundle IDs left in the code
+- [ ] Follows existing code conventions (see [CONTRIBUTING.md](../CONTRIBUTING.md))

CONTRIBUTING.md

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+# Contributing to macapptree
+
+Thank you for your interest in contributing! This document covers how to set up the project locally, the workflow for submitting changes, and our conventions.
+
+---
+
+## Prerequisites
+
+- macOS (the package uses macOS-only APIs)
+- Python 3.8 or later
+- Your terminal must have **Accessibility** permission granted in System Settings → Privacy & Security → Accessibility
+
+---
+
+## Development setup
+
+```bash
+# 1. Clone the repo
+git clone https://github.com/MacPaw/macapptree.git
+cd macapptree
+
+# 2. Create and activate a virtual environment
+python -m venv .venv
+source .venv/bin/activate
+
+# 3. Install with dev dependencies
+pip install -e ".[dev]"
+```
+
+---
+
+## Running tests
+
+```bash
+pytest
+```
+
+Since the library relies on live macOS Accessibility APIs, most tests require a running macOS session with the appropriate permissions. Tests that depend on a specific application being open are skipped automatically when that app is not available.
+
+---
+
+## Submitting changes
+
+1. Fork the repository and create a feature branch from `main`:
+   ```bash
+   git checkout -b feat/my-feature
+   ```
+2. Make your changes and commit with a clear message:
+   ```
+   feat: add support for AXSheet elements
+   fix: handle missing kCGWindowBounds gracefully
+   ```
+3. Open a pull request against `main` and fill in the PR template.
+
+---
+
+## Code conventions
+
+- Follow [PEP 8](https://peps.python.org/pep-0008/) style.
+- Keep public functions typed where practical.
+- No comments explaining *what* the code does — names should do that. Comments should only explain *why* (hidden constraints, workarounds, non-obvious invariants).
+- Keep pull requests focused: one logical change per PR.
+
+---
+
+## Reporting bugs
+
+Use [GitHub Issues](https://github.com/MacPaw/macapptree/issues). Include:
+
+- macOS version and Python version
+- Minimal reproducible example
+- Expected vs. actual behavior
+
+For security vulnerabilities, follow the process described in [SECURITY.md](SECURITY.md) instead.
+
+---
+
+## License
+
+By contributing, you agree that your contributions will be licensed under the [MIT License](LICENSE).