Added Material UI 4 import rule to package @backstage/integration-react

Signed-off-by: Juan Pablo Garcia Ripa <sarabadu@gmail.com>

packages/integration-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',
+  },
+});

packages/integration-react/dev/DevPage.tsx

@@ -15,7 +15,7 @@
  */
 
 import { ScmIntegration, ScmIntegrationsGroup } from '@backstage/integration';
-import { Typography } from '@material-ui/core';
+import Typography from '@material-ui/core/Typography';
 import React from 'react';
 import { scmIntegrationsApiRef } from '../src/ScmIntegrationsApi';