ensure cross_links is pluralized in config everywhere

Author: Mpdreamz

src/Elastic.Markdown/IO/Configuration/ConfigurationFile.cs

@@ -74,7 +74,7 @@ public ConfigurationFile(IFileInfo sourceFile, IDirectoryInfo rootPath, BuildCon
 							.Select(Glob.Parse)
 							.ToArray();
 						break;
-					case "cross_link":
+					case "cross_links":
 						CrossLinkRepositories = ReadStringArray(entry).ToArray();
 						break;
 					case "subs":

src/Elastic.Markdown/Myst/InlineParsers/DiagnosticLinkInlineParser.cs

@@ -166,8 +166,8 @@ private static void ProcessCrossLink(LinkInline link, InlineProcessor processor,
 		{
 			processor.EmitWarning(
 				link,
-				$"Cross link URI{uri}' is not allowed. Add '{scheme}' to the " +
-				$"'cross_link' list in the configuration file '{context.Configuration.SourceFile}' " +
+				$"Cross link '{uri}' is not allowed. Add '{scheme}' to the " +
+				$"'cross_links' list in the configuration file '{context.Configuration.SourceFile}' " +
 				"to allow cross links to this external documentation set."
 			);
 			return;

tests/Elastic.Markdown.Tests/MockFileSystemExtensions.cs

@@ -13,7 +13,7 @@ public static void GenerateDocSetYaml(this MockFileSystem fileSystem, IDirectory
 	{
 		// language=yaml
 		var yaml = new StringWriter();
-		yaml.WriteLine("cross_link:");
+		yaml.WriteLine("cross_links:");
         yaml.WriteLine("  - docs-content");
         yaml.WriteLine("  - kibana");
 		yaml.WriteLine("toc:");

tests/authoring/Framework/Setup.fs

@@ -40,7 +40,7 @@ type Setup =
     ) =
         let root = fileSystem.DirectoryInfo.New(Path.Combine(Paths.Root.FullName, "docs/"));
         let yaml = new StringWriter();
-        yaml.WriteLine("cross_link:");
+        yaml.WriteLine("cross_links:");
         yaml.WriteLine("  - docs-content");
         yaml.WriteLine("toc:");
         let markdownFiles = fileSystem.Directory.EnumerateFiles(root.FullName, "*.md", SearchOption.AllDirectories)