docs: deprecated Astro.props.slug → Astro.props.id (#2685)

Co-authored-by: HiDeoo <494699+HiDeoo@users.noreply.github.com>

Author: julien-deramond

docs/src/content/docs/guides/overriding-components.mdx

@@ -141,7 +141,7 @@ In the following example, a component overriding Starlight's [`Footer`](/referen
 import type { Props } from '@astrojs/starlight/props';
 import Default from '@astrojs/starlight/components/Footer.astro';
 
-const isHomepage = Astro.props.slug === '';
+const isHomepage = Astro.props.id === '';
 ---
 
 {