fix: explain XML stylesheet in dev

Author: harlan-zw

src/runtime/util/builder.ts

@@ -251,7 +251,7 @@ export function generateXslStylesheet() {
             Generated by <a href="https://github.com/harlan-zw/nuxt-simple-sitemap" target="_blank" rel="noopener">Nuxt
             Simple Sitemap</a>.
           </p>
-          ${process.dev ? '<div class="expl warn"><p><strong>Development preview</strong></p><p>In development, prerendered routes and data can not be displayed.</p><p>Make sure you test your production sitemap using <code>nuxi generate</code> or <code>nuxi build</code>.</p></div>' : ''}
+          ${process.dev ? '<div class="expl warn"><p><strong>Development preview</strong></p><p>URLs may be missing in development because there\'s no prerendering discovery. Make sure you test using <code>nuxi generate</code> or <code>nuxi build</code>.</p><p>Tip: You are looking at a XML stylesheet, if you want to see the raw sitemap as robots see it, please view the page source. You can disable the stylesheet using <code>xsl: false</code>. This alert is only displayed in development.</p></div>' : ''}
           <xsl:if test="count(sitemap:sitemapindex/sitemap:sitemap) &gt; 0">
             <p class="expl">
               This XML Sitemap Index file contains