mariadb: added support for .sql.zst in /docker-entrypoint-initdb.d

This was added a while ago in MariaDB/mariadb-docker#376

mariadb/content.md

@@ -145,7 +145,7 @@ Currently, this is only supported for `MARIADB_ROOT_PASSWORD`, `MARIADB_ROOT_HOS
 
 # Initializing a fresh instance
 
-When a container is started for the first time, a new database with the specified name will be created and initialized with the provided configuration variables. Furthermore, it will execute files with extensions `.sh`, `.sql`, `.sql.gz`, and `.sql.xz` that are found in `/docker-entrypoint-initdb.d`. Files will be executed in alphabetical order. `.sh` files without file execute permission are sourced rather than executed. You can easily populate your `%%IMAGE%%` services by [mounting a SQL dump into that directory](https://docs.docker.com/engine/tutorials/dockervolumes/#mount-a-host-file-as-a-data-volume) and provide [custom images](https://docs.docker.com/reference/builder/) with contributed data. SQL files will be imported by default to the database specified by the `MARIADB_DATABASE` / `MYSQL_DATABASE` variable.
+When a container is started for the first time, a new database with the specified name will be created and initialized with the provided configuration variables. Furthermore, it will execute files with extensions `.sh`, `.sql`, `.sql.gz`, `.sql.xz` and `.sql.zst` that are found in `/docker-entrypoint-initdb.d`. Files will be executed in alphabetical order. `.sh` files without file execute permission are sourced rather than executed. You can easily populate your `%%IMAGE%%` services by [mounting a SQL dump into that directory](https://docs.docker.com/engine/tutorials/dockervolumes/#mount-a-host-file-as-a-data-volume) and provide [custom images](https://docs.docker.com/reference/builder/) with contributed data. SQL files will be imported by default to the database specified by the `MARIADB_DATABASE` / `MYSQL_DATABASE` variable.
 
 # Caveats