Updates ECOSYSTEM with a new sample project (#1252)

ECOSYSTEM.md

@@ -42,6 +42,7 @@ If your project isn't listed here and you would like it to be, please feel free
 - [sandbox_axum_observability](https://github.com/davidB/sandbox_axum_observability) A Sandbox/showcase project to experiment axum and observability (tracing, opentelemetry, jaeger, grafana tempo,...)
 - [axum_admin](https://github.com/lingdu1234/axum_admin): An admin panel built with **axum**, Sea-orm and Vue 3.
 - [rgit](https://git.inept.dev/~doyle/rgit.git/about): A blazingly fast Git repository browser, compatible with- and heavily inspired by cgit.
+- [Petclinic](https://github.com/danipardo/petclinic): A port of Spring Framework's Petclinic showcase project to Axum
 
 [Realworld]: https://github.com/gothinkster/realworld
 [SQLx]: https://github.com/launchbadge/sqlx