Add ToHtml helper accepting a TextWriter

src/Markdig.Tests/TestMarkdigCoreApi.cs

@@ -74,6 +74,35 @@ namespace Markdig.Tests
             }
         }
 
+        [Test]
+        public void TestDocumentToHtmlWithWriter()
+        {
+            var writer = new StringWriter();
+
+            for (int i = 0; i < 5; i++)
+            {
+                MarkdownDocument document = Markdown.Parse("This is a text with some *emphasis*");
+                document.ToHtml(writer);
+                string html = writer.ToString();
+                Assert.AreEqual("<p>This is a text with some <em>emphasis</em></p>\n", html);
+                writer.GetStringBuilder().Length = 0;
+            }
+
+            writer = new StringWriter();
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseAdvancedExtensions()
+                .Build();
+
+            for (int i = 0; i < 5; i++)
+            {
+                MarkdownDocument document = Markdown.Parse("This is a text with a https://link.tld/", pipeline);
+                document.ToHtml(writer, pipeline);
+                string html = writer.ToString();
+                Assert.AreEqual("<p>This is a text with a <a href=\"https://link.tld/\">https://link.tld/</a></p>\n", html);
+                writer.GetStringBuilder().Length = 0;
+            }
+        }
+
         [Test]
         public void TestConvert()
         {

src/Markdig/Markdown.cs

@@ -132,6 +132,28 @@ namespace Markdig
             return renderer.Writer.ToString() ?? string.Empty;
         }
 
+        /// <summary>
+        /// Converts a Markdown document to HTML.
+        /// </summary>
+        /// <param name="document">A Markdown document.</param>
+        /// <param name="writer">The destination <see cref="TextWriter"/> that will receive the result of the conversion.</param>
+        /// <param name="pipeline">The pipeline used for the conversion.</param>
+        /// <returns>The result of the conversion</returns>
+        /// <exception cref="ArgumentNullException">if markdown document variable is null</exception>
+        public static void ToHtml(this MarkdownDocument document, TextWriter writer, MarkdownPipeline? pipeline = null)
+        {
+            if (document is null) ThrowHelper.ArgumentNullException(nameof(document));
+            if (writer is null) ThrowHelper.ArgumentNullException_writer();
+
+            pipeline ??= DefaultPipeline;
+
+            using var rentedRenderer = pipeline.RentHtmlRenderer(writer);
+            HtmlRenderer renderer = rentedRenderer.Instance;
+
+            renderer.Render(document);
+            renderer.Writer.Flush();
+        }
+
         /// <summary>
         /// Converts a Markdown string to HTML and output to the specified writer.
         /// </summary>