reintroduce bitty and add progressive enhancement and tabs

data/static/js/bits/ui.js

@@ -0,0 +1,25 @@
+export const b = {}
+
+export function setTab(_, sender, el) {
+  if (sender.ariaSelected === 'true') {
+    return;
+  }
+  if (!el.contains(sender)) {
+    return;
+  }
+  const tabIndex = parseInt(sender.dataset.tabIndex);
+  const tabPanels = el.querySelectorAll('.tab-content');
+  const tabButtons = el.querySelectorAll('.tab-bar button');
+
+  for (let i = 0; i < tabPanels.length; i++) {
+    const tabPanel = tabPanels[i];
+    const tabButton = tabButtons[i];
+    if (i === tabIndex) {
+      tabPanel.classList.remove('hidden');
+      tabButton.ariaSelected = 'true';
+    } else if (!tabPanel.classList.contains('hidden')) {
+      tabPanel.classList.add('hidden');
+      tabButton.ariaSelected = 'false';
+    }
+  }
+}