Add JetBrains as project user (#491)

Author: VladRassokhin

docs/index.md

@@ -24,6 +24,7 @@ TestContainers makes it easy to launch useful Docker containers for the duration
  * [Apache James](https://james.apache.org) - LDAP and Cassandra integration testing
  * [StreamSets](https://github.com/streamsets/datacollector) - LDAP, MySQL Vault, MongoDB, Redis integration testing
  * [Playtika](http://www.playtika.com) - Kafka, Couchbase, MariaDB, Redis, Neo4j, Aerospike, MemSQL
+ * [JetBrains](https://www.jetbrains.com/) - Testing of the TeamCity plugin for HashiCorp Vault
 
 ## License