Update content.md: execution order of initdb scripts (#649)

mysql/content.md

@@ -116,7 +116,7 @@ Sets root (*not* the user specified in `MYSQL_USER`!) user as expired once init
 
 # Initializing a fresh instance
 
-When a container is started for the first time, a new database `mysql` will be initialized with the provided configuration variables. Furthermore, it will execute files with extensions `.sh` and `.sql` that are found in `/docker-entrypoint-initdb.d`. You can easily populate your %%REPO%% services by [mounting a SQL dump into that directory](https://docs.docker.com/userguide/dockervolumes/#mount-a-host-file-as-a-data-volume) and provide [custom images](https://docs.docker.com/reference/builder/) with contributed data.
+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` and `.sql.gz` that are found in `/docker-entrypoint-initdb.d`. Files will be executed in alphabetical order. You can easily populate your %%REPO%% services by [mounting a SQL dump into that directory](https://docs.docker.com/userguide/dockervolumes/#mount-a-host-file-as-a-data-volume) and provide [custom images](https://docs.docker.com/reference/builder/) with contributed data.
 
 # Caveats