feat: implement basic server

This demo can:
- Serve a webpage
- Serve static assets
- Asynchronously fetch html

templates/fragment/table.html

@@ -0,0 +1,8 @@
+<thead>
+    <tr><th>foo</th><th>bar</th><th>baz</th></tr>
+</thead>
+<tbody>
+    {% for row in table %}
+    <tr><td>{{ row.foo }}</td><td>{{ row.bar }}</td><td>{{ row.baz }}</td></tr>
+    {% endfor %}
+</tbody>