Preinstall locale to enable local-gen for database localization

**Is your feature request related to a problem? Please describe.**
As a engineer who try to learn data engineering such as SQL on Studio Lab by [`ipython-sql`](https://github.com/catherinedevlin/ipython-sql) needs `local-gen` to setup the teaching materials because these depend on locale. For example [100knocks-preprocess](https://github.com/The-Japan-DataScientist-Society/100knocks-preprocess) depends on [`ja_JP.UTF-8`](https://github.com/The-Japan-DataScientist-Society/100knocks-preprocess/blob/master/dockerfiles/postgres/Dockerfile#L3).

The locale in Studio Lab is only a few.

```
(studiolab) studio-lab-user@default:~$ locale -a
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
C
C.UTF-8
POSIX
```

**Describe the solution you'd like**
Preinstall locale to enable local-gen

**Describe alternatives you've considered**
We can use default locale but the character data might be broken if we do not choose appropriate locale.

**Additional context**

None