Create PostgreSQL and MySQL databases at devcontainer

This pull request creates PostgreSQL and MySQL databases at devcontainer.

The current one runs the last exit even if the `activerecord` directory exists.

```
cd activerecord || echo "activerecord directory doesn't exist" && exit
```
As a result, `activerecord_unittest` or `activerecord_unittest2` are not created in both PostgreSQL
and MySQL.

- Without this commit: `activerecord_unittest` or `activerecord_unittest2` are not created

```sql
$ mysql -uroot -proot
... snip ...
MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.001 sec)
```

```sql
$ psql -d postgres
psql (17.4 (Debian 17.4-1.pgdg120+2))
Type "help" for help.

postgres=# \l
                                                    List of databases
   Name    |  Owner   | Encoding | Locale Provider |  Collate   |   Ctype    | Locale | ICU Rules |   Access privileges
-----------+----------+----------+-----------------+------------+------------+--------+-----------+-----------------------
 postgres  | postgres | UTF8     | libc            | en_US.utf8 | en_US.utf8 |        |           |
 template0 | postgres | UTF8     | libc            | en_US.utf8 | en_US.utf8 |        |           | =c/postgres          +
           |          |          |                 |            |            |        |           | postgres=CTc/postgres
 template1 | postgres | UTF8     | libc            | en_US.utf8 | en_US.utf8 |        |           | =c/postgres          +
           |          |          |                 |            |            |        |           | postgres=CTc/postgres
(3 rows)
```

Author: yahonda

.devcontainer/boot.sh

@@ -8,7 +8,7 @@ if [ -n "${NVM_DIR}" ]; then
   yarn install
 fi
 
-cd activerecord || echo "activerecord directory doesn't exist" && exit
+cd activerecord || { echo "activerecord directory doesn't exist"; exit; }
 
 # Create PostgreSQL databases
 bundle exec rake db:postgresql:rebuild