Add header objects and demo

src/file/document/body/section-properties/header-reference/header-reference-attributes.ts

@@ -0,0 +1,13 @@
+import { XmlAttributeComponent } from "file/xml-components";
+
+export interface IHeaderReferenceAttributes {
+    type: string;
+    id: string;
+}
+
+export class HeaderReferenceAttributes extends XmlAttributeComponent<IHeaderReferenceAttributes> {
+    protected xmlKeys = {
+        type: "w:type",
+        id: "r:id",
+    };
+}