chore: move signals client to fronend plugin

Signed-off-by: Heikki Hellgren <heikki.hellgren@op.fi>

plugins/signals/dev/index.tsx

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import React from 'react';
+import { createDevApp } from '@backstage/dev-utils';
+import { signalsPlugin } from '../src/plugin';
+import { Content, Header, Page } from '@backstage/core-components';
+import { Typography } from '@material-ui/core';
+
+createDevApp()
+  .registerPlugin(signalsPlugin)
+  .addPage({
+    title: 'Debug',
+    element: (
+      <Page themeId="home">
+        <Header title="Signals" />
+        <Content>
+          <Typography>TODO</Typography>
+        </Content>
+      </Page>
+    ),
+  })
+  .render();