Various modernizations and documentation updates

Applied automated security patches and code formatting updates

Updated webhook trigger to return 401 instead of throwing on invalid signature, restoring Xero's intent-to-receive validation handshake

Updated spectral version

Added New and Updated Records polling trigger that checks for new and updated invoices, contacts, bank transactions, and other accounting records in Xero on a configured schedule

Updated example payloads

Various modernizations and documentation updates

Improved input field documentation with formatted URL links for better readability

Enhanced webhook triggers to support simulated test executions

Added improved error handling for invalid webhook signatures to enhance security