Update README.md

README.md

@@ -381,6 +381,7 @@ Websites with lists of relays and their performance/health:
 - [nostr-launch](https://codeberg.org/rsbondi/nostr-launch) - a tool for launching a bunch of relays and clients locally for development and testing
 - [nostr-notify](https://github.com/jb55/nostr-notify)![stars](https://img.shields.io/github/stars/jb55/nostr-notify.svg?style=social) - desktop nostr notifications using libnotify
 - [nostr-proxy](https://github.com/dolu89/nostr-proxy)![stars](https://img.shields.io/github/stars/dolu89/nostr-proxy?style=social) - Push and get events to your Proxy, get results from multiple Nostr relays.
+- [nostr-post-checker](https://koteitan.github.io/nostr-post-checker/) - check if event exists on relays
 - [NostrP2P](https://github.com/ryogrid/nostrp2p)![stars](https://img.shields.io/github/stars/ryogrid/nostrp2p.svg?style=social) - Pure peer-to-peer distributed microblog system on NAT transparent overlay network implemented in Golang based on idea of Nostr
 - [nostr-rs-relay-compose](https://github.com/vdo/nostr-rs-relay-compose)![stars](https://img.shields.io/github/stars/vdo/nostr-rs-relay-compose.svg?style=social) - a Docker compose deployment for nostr-rs-relay with SSL support based on Traefik
 - [nostr-spam-detection](https://github.com/blakejakopovic/nostr-spam-detection)![stars](https://img.shields.io/github/stars/blakejakopovic/nostr-spam-detection.svg?style=social) - An experiment in building a machine learning model to label Nostr spam content for filtering and relay rejection.