graphiql: migrate to use plugin-api

Co-authored-by: Juan Lulkin <jmaiz@spotify.com>
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

plugins/graphiql/dev/index.tsx

@@ -16,7 +16,8 @@
 
 import React from 'react';
 import { createDevApp } from '@backstage/dev-utils';
-import { githubAuthApiRef, errorApiRef } from '@backstage/core';
+import { githubAuthApiRef, errorApiRef } from '@backstage/plugin-api';
+import GraphiQLIcon from '../src/assets/graphiql.icon.svg';
 import {
   graphiqlPlugin,
   GraphQLEndpoints,
@@ -55,6 +56,7 @@ createDevApp()
   })
   .addPage({
     title: 'GraphiQL',
+    icon: GraphiQLIcon,
     element: <GraphiQLPage />,
   })
   .render();