feat: add mailtrap-email-integration skill

[dieudonneAwa]

Adds a new skill covering transactional email sending via Mailtrap's Email API and SMTP.

Skill name: mailtrap-email-integration
Author: dieudonneAwa
Version: 1.0
Tags: email, api, smtp, integration, mailtrap

What this skill helps agents do:
Send transactional and bulk emails via Mailtrap's Email API or SMTP, including authentication, environment separation (sandbox vs production), domain verification, and delivery error handling.

Structure checklist:

• Skill is in a top-level folder (mailtrap-email-integration/)
• Folder contains a SKILL.md file
• SKILL.md includes valid YAML frontmatter (name, description, author, version, tags)

Security acknowledgement:

• Does not contain malicious behavior
• Does not attempt to exfiltrate secrets, tokens, or credentials
• Does not contain obfuscated payloads
• I understand all submissions run through automated security scanning

[github-actions]

✅ Validate Skills — PASSED

Summary: FAIL=0 · WARN=0
Changed skill dirs: mailtrap-email-integration

Output (last 200 lines)

✅ Found 8 skill directories.
✅ api-setup: structure validated
✅ beads: structure validated
✅ code-review: structure validated
✅ frontend-design: structure validated
✅ goose-blog-post: structure validated
✅ mailtrap-email-integration: structure validated
✅ rp-why: structure validated
✅ testing-strategy: structure validated

Structure validation PASSED.

[github-actions]

🛡️ Skills Security Scan — PASS

Summary: FAIL=0 · WARN=0 · FILES=1
Changed skills scanned: mailtrap-email-integration

✅ No issues detected.

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Notes: This comment auto-updates on each push to keep PRs clean.