fix: replace Buffer operations with string methods to resolve deprecation warning

[BrenoRev]

#30

Issue Fixed This change addresses the Node.js deprecation warning:

What Changed Replaced Buffer-based operations in the sanitize() function with pure string methods to eliminate deprecated Buffer constructor usage. The implementation now uses JavaScript's native string operations (split(), filter(), and join()) while maintaining the same XML character filtering behavior.

Benefits Eliminates deprecation warnings that were causing Lambda function failures Maintains the same output as the previous implementation Improves security by avoiding potential Buffer-related vulnerabilities Better handles edge cases (null/undefined values)