Add custom panel example using React (home-assistant#2651)

.gitignore

@@ -7,6 +7,7 @@ config/custom_components/*
 !config/custom_components/example.py
 !config/custom_components/hello_world.py
 !config/custom_components/mqtt_example.py
+!config/custom_components/react_panel
 
 tests/testing_config/deps
 tests/testing_config/home-assistant.log

config/custom_components/react_panel/__init__.py

@@ -0,0 +1,30 @@
+"""
+Custom panel example showing TodoMVC using React.
+
+Will add a panel to control lights and switches using React. Allows configuring
+the title via configuration.yaml:
+
+react_panel:
+  title: 'home'
+
+"""
+import os
+
+from homeassistant.components.frontend import register_panel
+
+DOMAIN = 'react_panel'
+DEPENDENCIES = ['frontend']
+
+PANEL_PATH = os.path.join(os.path.dirname(__file__), 'panel.html')
+
+
+def setup(hass, config):
+    """Initialize custom panel."""
+    title = config.get(DOMAIN, {}).get('title')
+
+    config = None if title is None else {'title': title}
+
+    register_panel(hass, 'react', PANEL_PATH,
+                   title='TodoMVC', icon='mdi:checkbox-marked-outline',
+                   config=config)
+    return True