feat: restrict boolean coercion

[edmundhung]

I think it would be too aggresive if conform coerce anything truthy to true. This restrict it to on only (i.e. the default value of checkbox). If there is a need to use custom value, it is better to be explicit:

import { conform, useForm } from '@conform-to/react';
import { parse } from '@conform-to/zod';
import { z } from 'zod';

const schema = z.object({
  confirmed: z.string().transform(value => value === 'yes'),
});

function Example() {
  const [form, { confirmed }] = useForm({
    onValidate({ formData }) {
      return parse(formData, { schema });
    },
  });

  return (
    <form {...form.props}>
      {/* Example 1: Custom checkbox value */}
      <div>
        <label>Confirm</label>
        <input {...conform.input(confirmed, { type: 'checkbox', value: 'yes' })} />
        <div>{confirmed.error}</div>
      </div>
      {/* Example 2: Confirmation text */}
      <div>
        <label>Type "yes" to confirm</label>
        <input {...conform.input(confirmed, { type: 'text' })} />
        <div>{confirmed.error}</div>
      </div>
      <button>Submit</button>
    </form>
  );
}

[cloudflare-workers-and-pages]

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Preview URL:	https://6cfedc5f.conform.pages.dev
Branch Preview URL:	https://restrict-boolean-coercion.conform.pages.dev

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