✨ Use JsonValue instead of unknown

[aaditmshah]

Both JSON.parse and .json() currently return unknown. This type is too general. We can use the more specific JsonValue type here. This allows users to consume the return value of these functions without having to use zod. However, users are still encouraged to validate and parse the result into another type since JsonValue is difficult to use.

type JsonValue = string | number | boolean | JsonValue[] | JsonObject | null;

type JsonObject = { [key: string]: JsonValue };

[mattpocock]

See #10