Wire up comboboxes

app/javascript/controllers/autofocus_controller.js

@@ -0,0 +1,16 @@
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  static targets = [ "element" ]
+
+  connect() {
+    this.observer = new IntersectionObserver(([entry]) => {
+      if (entry.isIntersecting) this.elementTarget.focus()
+    })
+    this.observer.observe(this.elementTarget)
+  }
+
+  disconnect() {
+    this.observer.disconnect()
+  }
+}