Custom attributes on links not resolved

[scarlachs]

The bug only happens when using the package @storyblok/richtext, in the deprecated package @storyblok/react it works as expected.

---

Expected Behavior

Custom attributes on links should be added correctly to the a tag, e.g. : <a href="https://www.storyblok.com" target="_self" rel="nofollow noopener">https://www.storyblok.com</a>

Current Behavior

The custom attributes are added as object to the custom attribute, e.g.: <a custom="[object Object]" target="_self" href="https://www.storyblok.com">https://www.storyblok.com</a>

Steps to Reproduce

1. Story with a richtext field
2. In the richtext have a link with some custom attributes like "rel: nofollow noopener"
3. Render the richtext and inspect output

import {
    richTextResolver,
    type StoryblokRichTextOptions,
} from "@storyblok/richtext";
import React from "react";

const options: StoryblokRichTextOptions<React.ReactElement> = {
    renderFn: React.createElement,
    keyedResolvers: true,
};

const { render } = richTextResolver<React.ReactElement>(options);

function Richtext({ blok }: { blok: any }) {
    return (
        <section>
            {render(blok.richtext)}
        </section>
    );
}

export default Richtext;