[Thread] add demoapp for Thread network APIs

A screenshot of the demo app:
![](https://screenshot.googleplex.com/AsiYKPzG4nJpr6x.png)

Bug: 273227725
Change-Id: I8d9bcf00bb54d3f152c436b56df919d967c5b71b
diff --git a/thread/demoapp/res/layout/nav_header.xml b/thread/demoapp/res/layout/nav_header.xml
new file mode 100644
index 0000000..b91fb9c
--- /dev/null
+++ b/thread/demoapp/res/layout/nav_header.xml
@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2023 The Android Open Source Project
+
+     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.
+-->
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:gravity="bottom"
+    android:orientation="vertical" >
+
+  <ImageView
+      android:id="@+id/nav_header_image"
+      android:layout_width="wrap_content"
+      android:layout_height="wrap_content"
+      android:paddingTop="@dimen/nav_header_vertical_spacing"
+      android:src="@drawable/ic_thread_wordmark" />
+</LinearLayout>