Node.js update

• Update npm packages (before: 40 vulnerabilities (3 low, 13 moderate, 23 high, 1 critical) after: 8 vulnerabilities (3 low, 1 moderate, 3 high, 1 critical)).
• Update code to use ESM imports, emailjs no longer supports CommonJS require
• Add .nvmrc to indicate support for node.js LTS v20.