📝(react) add RHF examples

Rework a bit the recent work made on RHF example to make some component
more generic, such as RhfSelect and RhfDatepicker, which is based on a
design using RHF context hooks to provide a seamless integration.

Fixes #144

packages/react/src/tests/reactHookFormUtils.tsx

@@ -1,26 +0,0 @@
-import { FieldValues, FormState } from "react-hook-form";
-
-export function getFieldState<FormValues extends FieldValues>(
-  field: keyof FormValues,
-  formState: FormState<FormValues>,
-) {
-  if (field in formState.errors) {
-    return "error";
-  }
-  return "default";
-}
-
-export function getFieldErrorMessage<FormValues extends FieldValues>(
-  field: keyof FormValues,
-  formState: FormState<FormValues>,
-): string {
-  const errorMessage = formState.errors[field]?.message;
-  if (!errorMessage) {
-    return "";
-  }
-  return errorMessage as string;
-}
-
-export function onSubmit<FormValues>(data: FormValues) {
-  alert(`Submited form values: ${JSON.stringify(data)}`);
-}