feat(isXsdAnyURI): add XML Schema anyURI validator

[MazenSamehR]

fixes: https://github.com/validatorjs/validator.js/issues/920

Summary

• adds isXsdAnyURI, covering XML Schema anyURI requirements (whitespace collapse, percent-encoding, RFC 3986 validation, IPv6/IPvFuture authority parsing)
• wires the validator into src/index.js and documents usage in README.md
• introduces extensive tests for valid/invalid absolute and relative references, malformed authorities, percent-encoding errors, and encodeURI failure scenarios

References

• W3C XML Schema Part 2: Datatypes – §3.2.17 anyURI
• RFC 3986: Uniform Resource Identifier (URI): Generic Syntax

Checklist

• [x] PR contains only changes related; no stray files, etc.
• [x] README updated (where applicable)
• [x] Tests written (where applicable)
• [x] References provided in PR (where applicable)