feature: add support to add mutiple sections to the document inc. headers and footers

- write missing tests

src/file/document/body/section-properties/page-size/page-size-attributes.ts

@@ -1,9 +1,14 @@
 import { XmlAttributeComponent } from "file/xml-components";
 
+export enum PageOrientation {
+    PORTRAIT = "portrait",
+    LANDSCAPE = "landscape",
+}
+
 export interface IPageSizeAttributes {
     width?: number;
     height?: number;
-    orientation?: string;
+    orientation?: PageOrientation;
 }
 
 export class PageSizeAttributes extends XmlAttributeComponent<IPageSizeAttributes> {