Merge pull request #341 from AlekSi/patch-1

Add FerretDB

Author: kmoppel

README.md

@@ -104,6 +104,7 @@ For Database Management
 * [Postgres-XL](https://www.postgres-xl.org/) - Scalable Open Source PostgreSQL-based Database Cluster.
 * [AgensGraph](https://bitnine.net/) - Powerful graph database based on the PostgreSQL.
 * [Greenplum Database](https://github.com/greenplum-db/gpdb) - Open source fork of PostgreSQL for large data volumes.
+* [FerretDB](https://www.ferretdb.io) - A truly Open Source MongoDB alternative on top of PostgreSQL.
 * [YugabyteDB](https://yugabyte.com/) - Open Source Distributed SQL using  a fork of PostgreSQL on top of distributed storage and transaction
 
 ### Monitoring