Scoped package @org/package ignored by import/order

### Config

"import/order": [
"error",
{
"groups": [
"builtin",
"external",
"internal",
"parent",
"sibling",
"index"
]
}
]

### Actual/no error

import { withStyles } from '@material-ui/core/styles';
import { required } from 'ra-core';
import React from 'react';
import { RadioButtonGroupInput, TextInput } from 'react-admin';
import { SimpleNestboxForm, NestboxEdit } from '../../../main/admin';
import styles from './styles';
import '@material-ui/icons/CheckCircle'; // <-- culprit

### Expected

import { withStyles } from '@material-ui/core/styles';
import '@material-ui/icons/CheckCircle';
import { required } from 'ra-core';
import React from 'react';
import { RadioButtonGroupInput, TextInput } from 'react-admin';
import { NestboxEdit, SimpleNestboxForm } from '../../../main/admin';
import styles from './styles';

I obtain the correct sorting by invoking `VSCode` `Organize imports`

Reproduce the reported ordering with the shown import/order configuration and imports, then trace the import/order rule entry point that classifies the scoped package import. Done means the side-effect import from @material-ui/icons/CheckCircle is placed with external imports in the expected order, without regressing the other groups.

Written by the indexing model from the issue text.