Add ESLint Rule to StackOverflow Plugin

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

plugins/stack-overflow/.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/stack-overflow/src/home/StackOverflowQuestions/Content.tsx

@@ -16,14 +16,12 @@
 
 import { useApi } from '@backstage/core-plugin-api';
 import { Link } from '@backstage/core-components';
-import {
-  IconButton,
-  List,
-  ListItem,
-  ListItemText,
-  ListItemSecondaryAction,
-  ListItemIcon,
-} from '@material-ui/core';
+import IconButton from '@material-ui/core/IconButton';
+import List from '@material-ui/core/List';
+import ListItem from '@material-ui/core/ListItem';
+import ListItemText from '@material-ui/core/ListItemText';
+import ListItemSecondaryAction from '@material-ui/core/ListItemSecondaryAction';
+import ListItemIcon from '@material-ui/core/ListItemIcon';
 import Typography from '@material-ui/core/Typography';
 import OpenInNewIcon from '@material-ui/icons/OpenInNew';
 import useAsync from 'react-use/lib/useAsync';

plugins/stack-overflow/src/home/StackOverflowQuestions/StackOverflowQuestions.stories.tsx

@@ -18,7 +18,7 @@ import { HomePageStackOverflowQuestions } from '../../plugin';
 import { wrapInTestApp, TestApiProvider } from '@backstage/test-utils';
 import { configApiRef } from '@backstage/core-plugin-api';
 import { ConfigReader } from '@backstage/config';
-import { Grid } from '@material-ui/core';
+import Grid from '@material-ui/core/Grid';
 import React, { ComponentType, PropsWithChildren } from 'react';
 import { StackOverflowIcon } from '../../icons';
 import { stackOverflowApiRef } from '../../api';

plugins/stack-overflow/src/search/StackOverflowSearchResultListItem/StackOverflowSearchResultListItem.tsx

@@ -16,14 +16,12 @@
 
 import React from 'react';
 import { Link } from '@backstage/core-components';
-import {
-  Divider,
-  ListItem,
-  ListItemText,
-  ListItemIcon,
-  Box,
-  Chip,
-} from '@material-ui/core';
+import Divider from '@material-ui/core/Divider';
+import ListItem from '@material-ui/core/ListItem';
+import ListItemText from '@material-ui/core/ListItemText';
+import ListItemIcon from '@material-ui/core/ListItemIcon';
+import Box from '@material-ui/core/Box';
+import Chip from '@material-ui/core/Chip';
 import { useAnalytics } from '@backstage/core-plugin-api';
 import type { ResultHighlight } from '@backstage/plugin-search-common';
 import { HighlightedSearchResultText } from '@backstage/plugin-search-react';