feat: add eslint rule for top level imports

Signed-off-by: Timothy Deakin <cftad@protonmail.com>

.changeset/sweet-planets-relate.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-org-react': patch
+---
+
+Added the `no-top-level-material-ui-4-imports` ESLint rule to aid with the migration to Material UI v5

plugins/org-react/.eslintrc.js

@@ -1 +1,5 @@
-module.exports = require('@backstage/cli/config/eslint-factory')(__dirname);
+module.exports = require('@backstage/cli/config/eslint-factory')(__dirname, {
+  rules: {
+    '@backstage/no-top-level-material-ui-4-imports': 'error',
+  },
+});

plugins/org-react/src/components/GroupListPicker/GroupListPickerButton.tsx

@@ -15,7 +15,9 @@
  */
 
 import React from 'react';
-import { makeStyles, Typography, Button } from '@material-ui/core';
+import Typography from '@material-ui/core/Typography';
+import Button from '@material-ui/core/Button';
+import { makeStyles } from '@material-ui/core/styles';
 import KeyboardArrowDownIcon from '@material-ui/icons/KeyboardArrowDown';
 import PeopleIcon from '@material-ui/icons/People';