Add basic Stimulus example

stimulus/basic.html

@@ -0,0 +1,24 @@
+<script type="module">
+  import { Application, Controller } from "https://unpkg.com/@hotwired/stimulus/dist/stimulus.js"
+
+  window.Stimulus = Application.start()
+
+  Stimulus.register("hello", class extends Controller {
+    static targets = [ "name", "output" ]
+
+    greet() {
+      this.outputTarget.textContent =
+        `Hello, ${this.nameTarget.value}!`
+    }
+  })
+</script>
+
+<div data-controller="hello">
+  <input data-hello-target="name" type="text">
+
+  <button data-action="click->hello#greet">
+    Greet
+  </button>
+
+  <span data-hello-target="output"></span>
+</div>