Add contribution guidelines and issue/PR templates

[stevenkiwanukakafeero]

The repository currently lacks structured contribution guidelines and templates.

Problem:
Contributors may not have clear direction on:

• How to contribute
• How to format issues and pull requests
• What standards to follow

Suggested solution:

1. Add a CONTRIBUTING.md file including:

   • Contribution workflow (fork → branch → PR)
   • Commit message format
   • Code style expectations

2. Add issue templates:

   • Bug report template
   • Feature request template

3. Add pull request template:

   • Description of changes
   • Linked issues
   • Testing checklist

Importance:
Templates and guidelines improve collaboration, maintain consistency, and make it easier for maintainers to review contributions.