test(draft2020-12): add literal Unicode coverage for pattern and patternProperties

[abhi-03-kh]

Summary

Adds literal Unicode test cases to pattern.json and patternProperties.json for draft-2020-12.

Technical Context

Draft-2020-12 requires Unicode-aware regular expression handling. These tests add simple literal Unicode cases (Greek letters and emoji) without relying on advanced regex features or engine-specific behavior.

The goal is to strengthen coverage around required Unicode semantics while keeping tests portable and spec-aligned.

Changes

• Added literal Greek character pattern tests (^λ+$)
• Added literal emoji pattern test (^😊$)
• Added corresponding patternProperties coverage using literal Unicode property names

Validation

Validated JSON integrity locally using Node.js:

node -e "JSON.parse(require('fs').readFileSync('tests/draft2020-12/pattern.json','utf8'))"
node -e "JSON.parse(require('fs').readFileSync('tests/draft2020-12/patternProperties.json','utf8'))"

[abhi-03-kh]

Given the ongoing discussion in #837 around Unicode regex semantics for draft-2020-12, I’m happy to narrow or adapt this PR if needed to avoid duplication. My intent here was to add simple literal Unicode coverage without entering into the broader optional test cleanup.