Also initialize additionalLabels HashSet with StringComparer.OrdinalIgnoreCase

Author: reakaleek

src/Elastic.Markdown/IO/MarkdownFile.cs

@@ -50,10 +50,10 @@ public string? NavigationTitle
 	}
 
 	//indexed by slug
-	private readonly Dictionary<string, PageTocItem> _tableOfContent = new Dictionary<string, PageTocItem>(StringComparer.OrdinalIgnoreCase);
+	private readonly Dictionary<string, PageTocItem> _tableOfContent = new(StringComparer.OrdinalIgnoreCase);
 	public IReadOnlyDictionary<string, PageTocItem> TableOfContents => _tableOfContent;
 
-	private readonly HashSet<string> _additionalLabels = new();
+	private readonly HashSet<string> _additionalLabels = new(StringComparer.OrdinalIgnoreCase);
 	public IReadOnlySet<string> AdditionalLabels => _additionalLabels;
 
 	public string FilePath { get; }

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

@@ -136,7 +136,7 @@ public override bool Match(InlineProcessor processor, ref StringSlice slice)
 			if (!string.IsNullOrEmpty(anchor))
 			{
 				if (markdown == null || (!markdown.TableOfContents.TryGetValue(anchor, out var heading)
-					&& !markdown.AdditionalLabels.Contains(anchor, StringComparer.OrdinalIgnoreCase)))
+					&& !markdown.AdditionalLabels.Contains(anchor)))
 					processor.EmitError(line, column, length, $"`{anchor}` does not exist in {markdown?.FileName}.");
 
 				else if (link.FirstChild == null && heading != null)