docs: update site for context-based media discovery (#1018)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Darius Cepulis <dcepulis@mux.com>

site/src/docs.config.ts

@@ -77,6 +77,7 @@ export const sidebar: Sidebar = [
         contents: [
           { slug: 'reference/render-element' },
           { slug: 'reference/use-button' },
+          { slug: 'reference/use-container-attach' },
           { slug: 'reference/use-media-attach' },
           { slug: 'reference/use-player-context' },
           { slug: 'reference/use-selector' },
@@ -96,6 +97,7 @@ export const sidebar: Sidebar = [
         defaultOpen: false,
         contents: [
           { slug: 'reference/container-mixin' },
+          { slug: 'reference/media-attach-mixin' },
           { slug: 'reference/player-context' },
           { slug: 'reference/provider-mixin' },
           { slug: 'reference/snapshot-controller' },