Fix markdown parser crash on inline HTML elements

src/Libraries/Microsoft.Extensions.DataIngestion.Markdig/MarkdownParser.cs

@@ -228,6 +228,10 @@ private static IngestionDocumentSection MapQuoteBlock(QuoteBlock quoteBlock, boo
             {
                 content.Append(codeInline.Content);
             }
+            else if (inline is HtmlInline htmlInline)
+            {
+                content.Append(htmlInline.Tag);
+            }
             else
             {
                 throw new NotSupportedException($"Inline type '{inline.GetType().Name}' is not supported.");

test/Libraries/Microsoft.Extensions.DataIngestion.Tests/Readers/MarkdownReaderTests.cs

@@ -133,6 +133,32 @@ public async Task SupportsTablesWithImages()
         Assert.Equal("Latest logo", img.AlternativeText);
     }
 
+    [ConditionalFact]
+    public async Task SupportsInlineHtml()
+    {
+        string markdownContent = "This has <sup>[1]</sup> inline HTML.";
+
+        IngestionDocument document = await ReadAsync(markdownContent);
+
+        var paragraph = Assert.Single(document.EnumerateContent().OfType<IngestionDocumentParagraph>());
+        Assert.Equal("This has <sup>[1]</sup> inline HTML.", paragraph.Text);
+        Assert.Equal(markdownContent, paragraph.GetMarkdown());
+    }
+
+    [ConditionalFact]
+    public async Task SupportsMultipleInlineHtmlElements()
+    {
+        string markdownContent = """
+        Text with <strong>bold</strong>, <em>italic</em>, <sub>subscript</sub>, and <sup>superscript</sup> tags.
+        """;
+
+        IngestionDocument document = await ReadAsync(markdownContent);
+
+        var paragraph = Assert.Single(document.EnumerateContent().OfType<IngestionDocumentParagraph>());
+        Assert.Equal("Text with <strong>bold</strong>, <em>italic</em>, <sub>subscript</sub>, and <sup>superscript</sup> tags.", paragraph.Text);
+        Assert.Equal(markdownContent, paragraph.GetMarkdown());
+    }
+
     private async Task<IngestionDocument> ReadAsync(string content)
     {
         using MemoryStream stream = new(System.Text.Encoding.UTF8.GetBytes(content));