Force allow the root page to be indexed (#1548)

* Force allow the root page to be indexed

Author: cotti

src/Elastic.Markdown/HtmlWriter.cs

@@ -135,7 +135,7 @@ private async Task<RenderResult> RenderLayout(MarkdownFile markdown, MarkdownDoc
 			UrlPathPrefix = markdown.UrlPathPrefix,
 			AppliesTo = markdown.YamlFrontMatter?.AppliesTo,
 			GithubEditUrl = editUrl,
-			AllowIndexing = DocumentationSet.Context.AllowIndexing && (markdown is DetectionRuleFile || !current.Hidden),
+			AllowIndexing = DocumentationSet.Context.AllowIndexing && (markdown.CrossLink.Equals("docs-content://index.md", StringComparison.OrdinalIgnoreCase) || markdown is DetectionRuleFile || !current.Hidden),
 			CanonicalBaseUrl = DocumentationSet.Context.CanonicalBaseUrl,
 			GoogleTagManager = DocumentationSet.Context.GoogleTagManager,
 			Features = DocumentationSet.Configuration.Features,