feat: add useFormattedISODate helper function

src/util.ts

 import { cloneDeep, isEqual } from 'lodash'
 import { computed, ComputedGetter, ComputedRef, readonly, Ref, ref, watch, watchEffect } from 'vue'
+import { formatISO, parseISO } from 'date-fns'
 
 export function computedIter<T>(fn: ComputedGetter<Iterable<T>>): ComputedRef<T[]> {
   return computed(() => Array.from(fn()))
@@ -47,3 +48,14 @@ export function useUpdatableState<T>(
   )
   return localRef
 }
+
+export function useFormattedISODate(date: Ref<Date>) {
+  return computed({
+    get() {
+      return formatISO(date.value, { representation: 'date' })
+    },
+    set(dateValue: string) {
+      date.value = parseISO(dateValue)
+    },
+  })
+}