added constant for dotnet generators.

Author: HugoMario

modules/swagger-codegen/src/main/java/io/swagger/codegen/v3/CodegenConstants.java

@@ -215,6 +215,8 @@ public static enum ENUM_PROPERTY_NAMING_TYPE {camelCase, PascalCase, snake_case,
     public static final String GENERATE_PROPERTY_CHANGED = "generatePropertyChanged";
     public static final String GENERATE_PROPERTY_CHANGED_DESC = "Specifies that models support raising property changed events.";
 
+    public static final String PRESERVE_COMMENT_NEWLINES = "preserveNewlinesInComments";
+
     public static final String NON_PUBLIC_API = "nonPublicApi";
     public static final String NON_PUBLIC_API_DESC = "Generates code with reduced access modifiers; allows embedding elsewhere without exposing non-public API calls to consumers.";