How to include a xsl stylesheet?

I am trying to include my xsl stylesheet but somehow it doesn't work.

**My code:**

```js
xml(
{
"?xml-stylesheet": [{ _attr: { type: "text/xsl", href: "sitemap.xsl" } }],
sitemapindex: [
{ _attr: { xmlns: "http://www.sitemaps.org/schemas/sitemap/0.9" } },
{ sitemap: [
{ loc: "https://nextjs.marcofranssen.nl/blog-sitemap.xml" },
{ lastmod: new Date().toISOString() },
]
],
},
{ declaration: true }
)
```

**Result:**

```xml

```

**Expected:**

```xml

https://nextjs.marcofranssen.nl/blog-sitemap.xml
2021-01-24T12:55:02.245Z

```