feat: AddRange for markers (#40)

Co-authored-by: Gerhard Olsson <gerhardol@users.noreply.github.com>

Project/Src/Document/MarkerStrategy/MarkerStrategy.cs

@@ -34,6 +34,12 @@ namespace ICSharpCode.TextEditor.Document
             textMarker.Add(item);
         }
 
+        public void AddMarker(IList<TextMarker> items)
+        {
+            markersTable.Clear();
+            textMarker.AddRange(items);
+        }
+
         public void InsertMarker(int index, TextMarker item)
         {
             markersTable.Clear();
@@ -109,4 +115,4 @@ namespace ICSharpCode.TextEditor.Document
             Document.UpdateSegmentListOnDocumentChange(textMarker, e);
         }
     }
-}
+}