Duplicate urls returned by `generateRemixSitemap` using React Router 7

Hi @AlemTuzlak, first of thanks for the package!

I do not know if its only related to RR7 or Remix v2 aswell, but when I use the following code to generate the sitemap, the `generateRemixSitemap` helper function returns duplicate links. Any chance to fix this or do you know why that is happening?

```ts
import { generateRemixSitemap } from "@forge42/seo-tools/remix/sitemap";
import type { Route } from "./+types/sitemap.xml";
import { href } from "react-router";

export const loader = async ({ request }: Route.LoaderArgs) => {
const { routes } = await import("virtual:react-router/server-build");
const sitemap = await generateRemixSitemap({
domain: new URL(request.url).origin,
ignore: [href("/api/chat"), href("/legal-notice"), href("/privacy-policy")],
// @ts-expect-error Type mismatch, maybe related to a stricter type mentioned in release notes for v.7.0.0
// https://github.com/forge-42/seo-tools/issues/8
routes,
});

return new Response(sitemap, {
headers: {
"Content-Type": "application/xml",
},
});
};
```

```ts
// routes.ts
import {
type RouteConfig,
index,
layout,
prefix,
route,
} from "@react-router/dev/routes";

export default [
layout("routes/layout.tsx", [
index("routes/index.tsx"),
...
route("sitemap.xml", "routes/sitemap.xml.ts"),
route("robots.txt", "routes/robots.txt.ts"),
]),
] satisfies RouteConfig;

```

The generated sitemap:

```xml

http://localhost:5173/

http://localhost:5173/

http://localhost:5173/chat

http://localhost:5173/blog

http://localhost:5173/

```