Add ability to create refs for Cloud Storage

[deptyped]

<script lang="ts" setup>
import { useWebAppCloudStorage } from 'vue-tg'

const valueRef = useWebAppCloudStorageItem<T>("some-key", "initial value", {
  writeDebounce: 500, // ms
  serializer: {
    read(raw: string): T
    write(value: T): string
  },
  onError: (error: unknown) => void,
})

valueRef.value = "another value"
</script>