Add PTO & Leave Policy agent skill example

[srivilliamsai]

What this PR adds or changes

Adds a new community Agent Skill (examples/pto-policy-agent-skill) that teaches an AI agent how to answer employee questions about Paid Time Off (PTO), annual accrual tiers, year-end rollover limits, and sick leave policy with clear escalation rules and Workday navigation steps.

Checklist for new or changed examples

• The example lives entirely in its own folder under examples/
• node scripts/validate-examples.mjs --check passes (valid example.json, README present, index table in sync)
• The README says what the artifact is and how to use it
• No credentials, tenant names, or real personal data anywhere in the folder

Anything reviewers should know?

N/A — Standard markdown-based agent skill template following the format established by expense-policy-agent-skill.