feat(esl-utils): focus order utility

src/modules/esl-utils/dom/focus.ts

@@ -0,0 +1,19 @@
+import {TAB} from './keys';
+
+/**
+ * Chain focus order between two elements.
+ * Passive (should be called inside keyboard event handler)
+ */
+export const handleFocusChain = (e: KeyboardEvent, first: HTMLElement, last: HTMLElement) => {
+  if (e.key !== TAB ) return;
+  if (last && e.target === first && e.shiftKey) {
+    last.focus();
+    e.preventDefault();
+    return true;
+  }
+  if (first && e.target === last && !e.shiftKey) {
+    first.focus();
+    e.preventDefault();
+    return true;
+  }
+};