fix: validate URI scheme grammar

[mcollina]

Summary

• validate parsed schemes against the ASCII grammar from RFC 3986 §3.1
• stop percent-decoding scheme text
• preserve malformed scheme input during normalization, reject it during equality checks, and throw during resolution
• add coverage for percent-encoded, invalid-leading-character, invalid-character, and Unicode case-folding forms

This addresses the behavior reported in GHSA-9pcr-hcx9-jj65 as an RFC compliance bug. No supported security-sensitive execution or navigation flow is involved.

Tests

• npm test
• npm run lint
• npm run test:typescript

[Tony133]

There are conflicts on the index.js file