Node.js v20+ support due to Vercel v18 deprecation

Vercel is deprecating Node.js v18 (announcement), with automatic upgrades to Node.js v20+ starting soon.

Isgithub-readme-streak-stats fully compatible with Node.js v20+? I don't think so because I tried redeploying with v20 and the build failed.

• Are there any known compatibility issues?
• Is there a plan to update or test for v20+?
• Should users deploying custom endpoints on Vercel expect any breakage?

Happy to help test or submit a PR if needed — want to confirm support ahead of the migration.