feat(vue): expand @robonen/vue composable collection

Composables, tests, category barrels, and README for @robonen/vue.

vue/toolkit/src/composables/elements/useFocusGuard/index.ts

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+import { focusGuard } from '@robonen/platform/browsers';
+import { onMounted, onUnmounted } from 'vue';
+
+// Global counter to drop the focus guards when the last instance is unmounted
+let counter = 0;
+
+/**
+ * @name useFocusGuard
+ * @category Elements
+ * @description Adds a pair of focus guards at the boundaries of the DOM tree to ensure consistent focus behavior
+ *
+ * @param {string} [namespace] - A namespace to group the focus guards
+ * @returns {void}
+ *
+ * @example
+ * useFocusGuard();
+ *
+ * @example
+ * useFocusGuard('my-namespace');
+ *
+ * @since 0.0.2
+ */
+export function useFocusGuard(namespace?: string) {
+  const manager = focusGuard(namespace);
+
+  const createGuard = () => {
+    manager.createGuard();
+    counter++;
+  };
+
+  const removeGuard = () => {
+    if (counter <= 1)
+      manager.removeGuard();
+
+    counter = Math.max(0, counter - 1);
+  };
+
+  onMounted(createGuard);
+  onUnmounted(removeGuard);
+}