Add `MutableText::AppendLineBreak()` method

sources/Text/MutableText.uc

@@ -19,6 +19,8 @@
  */
 class MutableText extends Text;
 
+var private int CODEPOINT_NEWLINE;
+
 //      Every formatted `string` essentially consists of multiple differently
 //  formatted (colored) parts. Such `string`s will be more convenient for us to
 //  work with if we separate them from each other.
@@ -96,6 +98,17 @@ public final function ToUpper()
     ConvertCase(false);
 }
 
+/**
+ *  Appends new line character to the caller `MutableText`.
+ *
+ *  @return Caller `MutableText` to allow for method chaining.
+ */
+public final function MutableText AppendLineBreak()
+{
+    AppendCodePoint(CODEPOINT_NEWLINE);
+    return self;
+}
+
 /**
  *  Appends contents of another `Text` to the caller `MutableText`.
  *
@@ -463,4 +476,5 @@ public final function MutableText ChangeFormatting(
 
 defaultproperties
 {
+    CODEPOINT_NEWLINE = 10
 }