Adds -n support for phpcs.

Do not print warnings (shortcut for --warning-severity=0)

This is handy to suppress `phpcs` warnings (triggered by `TODO` comments)

```
--------------------------------------------------------------------------------
FOUND 0 ERROR(S) AND 1 WARNING(S) AFFECTING 1 LINE(S)
--------------------------------------------------------------------------------
 151 | WARNING | Comment refers to a TODO task "Remove / reimplement
     |         | getDataSource()->value"
--------------------------------------------------------------------------------
```