Added new @backstage/no-top-level-mui4-imports rule

Signed-off-by: Andre Wanlin <awanlin@spotify.com>

plugins/linguist/.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-mui4-imports': 'error',
+  },
+});

plugins/linguist/src/components/LinguistCard/LinguistCard.tsx

@@ -14,15 +14,12 @@
  * limitations under the License.
  */
 
-import {
-  Box,
-  Chip,
-  Tooltip,
-  Typography,
-  makeStyles,
-  Grid,
-  useTheme,
-} from '@material-ui/core';
+import Box from '@material-ui/core/Box';
+import Chip from '@material-ui/core/Chip';
+import Tooltip from '@material-ui/core/Tooltip';
+import Typography from '@material-ui/core/Typography';
+import Grid from '@material-ui/core/Grid';
+import { makeStyles, useTheme } from '@material-ui/core/styles';
 import { InfoCard, Progress } from '@backstage/core-components';
 import Alert from '@material-ui/lab/Alert';
 import { DateTime } from 'luxon';