add simple-host example

examples/simple-host/example-host-react.html

@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<html lang="en">
+    <head>
+        <meta charset="UTF-8">
+        <meta name="viewport" content="width=device-width, initial-scale=1.0">
+        <style>
+            * {
+                box-sizing: border-box;
+            }
+            body {
+                margin: 0;
+                font-family: system-ui, -apple-system, sans-serif;
+            }
+        </style>
+        <title>Example MCP-UI React Host</title>
+    </head>
+    <body>
+        <div id="root"></div>
+        <script src="/src/example-host-react.tsx" type="module"></script>
+    </body>
+</html>