add: some styles and more organization

src/client/Counter.jsx

@@ -0,0 +1,13 @@
+import { useState } from 'preact/hooks'
+
+export const Counter = ({}) => {
+    const [count, setCount] = useState(0)
+
+    return (
+        <div class="counter">
+            <button onClick={() => setCount(value => value - 1)}>-</button>
+            <div class="value">{count}</div>
+            <button onClick={() => setCount(value => value + 1)}>+</button>
+        </div>
+    )
+}