Improve multiple argument example in README

[shuding]

We shouldn't recommend useMemo(() => ({ id }), [id]). It's not elegant, and the cache is not-reusable.

For example id changes from 1 → 2 → 1, and the cache can not be reused since A !== C:

const A = useMemo(() => ({ id: 1 }), [1])
const B = useMemo(() => ({ id: 2 }), [2])
const C = useMemo(() => ({ id: 1 }), [1])