CREATE SCHEMA as an alias for CREATE DATABASE

According to https://dev.mysql.com/doc/refman/8.0/en/create-database.html, CREATE SCHEMA is a synonym for CREATE DATABASE.

```
$ ./vendor/bin/lint-query --query 'create schema foo'
#1: The name of the entity was expected. (near "schema" at position 7)
$ ./vendor/bin/lint-query --query 'create database  foo'
$
```