Add OpenSSF Baseline compliance files

[mlieberman85]

Summary

This PR adds compliance files for OpenSSF Baseline:

• Add .github/CODEOWNERS with project maintainers
• Add MAINTAINERS.md documenting maintainers
• Add GOVERNANCE.md for project governance
• Add SUPPORT.md for support information
• Add .github/ISSUE_TEMPLATE/bug_report.md issue template
• Update SECURITY.md with VEX policy section
• Add .github/dependabot.yml configuration

Audit Results

After remediation:

• ✅ Pass: 34
• ❌ Fail: 3 (CHANGELOG.md, THREAT_MODEL.md, GitHub CLI issue)
• ⚠️ Needs Verification: 25

Test Plan

• Verify CODEOWNERS file is recognized by GitHub
• Verify issue template appears when creating new issues
• Re-run OpenSSF Baseline audit to confirm improvements