append()/getAll() support for `useSearchParams`

[cofl]

Describe the feature in detail (code, mocks, or screenshots encouraged)

An option that, if enabled, serializes arrays using the browser's native multiple-search-parameter support. This might be a boolean, or an iterable of affected keys.

const schema = v.object({
    regions: v.optional(v.fallback(v.array(v.picklist([ "na", "eu", "ocx" ])), []), [])
})
const params = useSearchParams(schema, { useAppendedArrays: true })
// can now handle ?region=na&region=eu

What type of pull request would this be?

Enhancement

Provide relevant links or additional information.

• https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams/append
• https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams/getAll