Added Material UI 4 import rule to plugins/rollbar

Signed-off-by: Aditya Kumar <aditya.kumar60@infosys.com>

plugins/rollbar/.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/rollbar/src/components/RollbarTopItemsTable/RollbarTopItemsTable.tsx

@@ -14,8 +14,9 @@
  * limitations under the License.
  */
 
-import { Box, Typography } from '@material-ui/core';
-import { Alert } from '@material-ui/lab';
+import Box from '@material-ui/core/Box';
+import Typography from '@material-ui/core/Typography';
+import Alert from '@material-ui/lab/Alert';
 import React from 'react';
 import {
   RollbarFrameworkId,