don't warn of language is empty

Author: Mpdreamz

src/Elastic.Markdown/Myst/CodeBlocks/EnhancedCodeBlockParser.cs

@@ -87,7 +87,7 @@ public override bool Close(BlockProcessor processor, Block block)
 			"terminal" => "bash",
 			_ => codeBlock.Language
 		};
-		if (!CodeBlock.Languages.Contains(codeBlock.Language))
+		if (!string.IsNullOrEmpty(codeBlock.Language) && !CodeBlock.Languages.Contains(codeBlock.Language))
 			codeBlock.EmitWarning($"Unknown language: {codeBlock.Language}");
 
 		var lines = codeBlock.Lines;

src/Elastic.Markdown/Myst/CodeBlocks/SupportedLanguages.cs

@@ -182,7 +182,7 @@ public static class CodeBlock
 	};
 
 
-	public static HashSet<string> Languages => new HashSet<string>(
+	public static HashSet<string> Languages => new(
 		LanguageMapping.Keys
 			.Concat(LanguageMapping.Values
 				.SelectMany(v => v.Split(',').Select(a => a.Trim()))