Chore: Migrate issue templates to YAML, update PR template, and add SECURITY.md

[cariasj03]

Description

This PR updates the issue and pull request templates to improve clarity and consistency, and adds a SECURITY.md file to enable GitHub's built-in vulnerability reporting flow. Issue templates were migrated from .md files to .yml format to support structured forms and better guidance for contributors.

Motivation & Context

The previous issue templates were freeform Markdown and lacked validation or structure. Migrating to YAML-based forms provides a better user experience when submitting issues and ensures key information is consistently collected.
Adding a SECURITY.md file enables the "Report a security vulnerability" option on the Issues page and provides a clear channel for responsible disclosure.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Refactoring (non-breaking change with no user-facing impact)
• Breaking change (fix or feature that changes existing behavior)
• Documentation update

Related Issues

N/A

Testing

Changes are limited to documentation. Verified that:

• External file links (CONTRIBUTING.md) are accessible from the GitHub UI preview.
• Using the YAML extension for VS Code to validate that all .yml files are free of syntax errors.
• Markdown renders as expected in GitHub.

Checklist

• I have read the contributing guidelines
• My code follows the style guidelines for this project
• I have commented important parts of the code
• I have made necessary updates to the documentation
• I have added or updated tests to prove my changes work
• All tests pass locally
• This PR does not introduce new warnings or console errors

Additional Notes

The content of the SECURITY.md file was discussed with and approved by our SecOps engineer, @dagerzuniga, to ensure alignment with internal security reporting processes.