Allow readonly arrays on `Value` type

We're using types generated via OpenAPI, which results with some nested types like `tags: readonly string[]`. This is not allowed by the current `Value` type from `@electric-sql/client`.

We would like to see support for readonly arrays too.
```typescript
export type Value =
| string
| number
| boolean
| bigint
| null
| Extensions
| Value[]
+ | readonly Value[]
| { [key: string]: Value }
```