Add details of pgTAP container image

Author: DavidGregory084

README.md

@@ -43,7 +43,7 @@ In order to run pgTAP tests with *pgtap-java*, you must extend the [PgTapTest](.
 
 `PgTapTest` requires 3 constructor parameters:
 
-* `database: PostgreSQLContainer<?>` - a [Testcontainers PostgreSQL](https://java.testcontainers.org/modules/databases/postgres/) database container.
+* `database: PostgreSQLContainer<?>` - a [Testcontainers PostgreSQL](https://java.testcontainers.org/modules/databases/postgres/) database container. This container image must have pgTAP preinstalled. See our [postgres-with-pgtap](https://github.com/opencastsoftware/postgres-with-pgtap/blob/main/Containerfile) Containerfile for an example of how you can do that.
 * `pgTapTestPath: Path` - the path to your pgTAP `.sql` test files
 * `pgTapTmpPath: Path` - the path where the pgTAP `.sql` test files will be mounted inside the PostgreSQL container.
 
@@ -59,4 +59,4 @@ This project wouldn't exist without the work of [theory](https://github.com/theo
 
 ## License
 
-All code in this repository is licensed under the Apache License, Version 2.0. See [LICENSE](./LICENSE).
+All code in this repository is licensed under the Apache License, Version 2.0. See [LICENSE](./LICENSE).