improve accessibility

app/javascript/elements/modal_button.js

@@ -0,0 +1,18 @@
+export default class extends HTMLElement {
+  connectedCallback () {
+    const dialog = document.getElementById(this.dataset.target)
+
+    this.querySelector('button').addEventListener('click', () => {
+      if (dialog) {
+        dialog.inert = false
+        dialog.showModal()
+      }
+    })
+
+    if (dialog) {
+      dialog.addEventListener('close', () => {
+        dialog.inert = true
+      })
+    }
+  }
+}