add sero to ECOSYSTEM.md (#2290)

ECOSYSTEM.md

@@ -74,6 +74,7 @@ If your project isn't listed here and you would like it to be, please feel free
 - [httq](https://github.com/scotow/httq) HTTP to MQTT trivial proxy.
 - [ReductStore](https://github.com/reductstore/reductstore): A time series database for storing and managing large amounts of blob data
 - [randoku](https://github.com/stchris/randoku): A tiny web service which generates random numbers and shuffles lists randomly
+- [sero](https://github.com/clowzed/sero): Host static sites with custom subdomains as surge.sh does. But with full control and cool new features. (axum, sea-orm, postgresql)
 
 [Realworld]: https://github.com/gothinkster/realworld
 [SQLx]: https://github.com/launchbadge/sqlx