Add support for escape characters for normalize (#155)

src/Markdig/Parsers/Inlines/EscapeInlineParser.cs

@@ -31,7 +31,8 @@ namespace Markdig.Parsers.Inlines
                     Content = new StringSlice(slice.Text, slice.Start, slice.Start),
                     Span = { Start = processor.GetSourcePosition(startPosition, out line, out column) },
                     Line = line,
-                    Column = column
+                    Column = column,
+                    IsFirstCharacterEscaped = true,
                 };
                 processor.Inline.Span.End = processor.Inline.Span.Start + 1;
                 slice.NextChar();
@@ -44,6 +45,7 @@ namespace Markdig.Parsers.Inlines
                 processor.Inline = new LineBreakInline()
                 {
                     IsHard = true,
+                    IsBackslash = true,
                     Span = { Start = processor.GetSourcePosition(startPosition, out line, out column) },
                     Line = line,
                     Column = column

src/Markdig/Renderers/Normalize/Inlines/LineBreakInlineRenderer.cs

@@ -20,9 +20,8 @@ namespace Markdig.Renderers.Normalize.Inlines
         {
             if (obj.IsHard)
             {
-                renderer.Write("  ");
+                renderer.Write(obj.IsBackslash ? "\\" : "  ");
             }
-
             renderer.WriteLine();
         }
     }

src/Markdig/Renderers/Normalize/Inlines/LiteralInlineRenderer.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
+
+using Markdig.Helpers;
 using Markdig.Syntax.Inlines;
 
 namespace Markdig.Renderers.Normalize.Inlines
@@ -13,6 +15,10 @@ namespace Markdig.Renderers.Normalize.Inlines
     {
         protected override void Write(NormalizeRenderer renderer, LiteralInline obj)
         {
+            if (obj.IsFirstCharacterEscaped && obj.Content.Length > 0 && obj.Content[obj.Content.Start].IsAsciiPunctuation())
+            {
+                renderer.Write('\\');
+            }
             renderer.Write(ref obj.Content);
         }
     }

src/Markdig/Syntax/Inlines/LineBreakInline.cs

@@ -10,5 +10,7 @@ namespace Markdig.Syntax.Inlines
     public class LineBreakInline : LeafInline
     {
         public bool IsHard { get; set; }
+
+        public bool IsBackslash { get; set; }
     }
 }

src/Markdig/Syntax/Inlines/LiteralInline.cs

@@ -48,6 +48,11 @@ namespace Markdig.Syntax.Inlines
         /// </summary>
         public StringSlice Content;
 
+        /// <summary>
+        /// A boolean indicating whether the first character of this literal is escaped by `\`.
+        /// </summary>
+        public bool IsFirstCharacterEscaped { get; set; }
+
         public override string ToString()
         {
             return Content.ToString();