Work on moving Document into its own wrapper

src/file/paragraph/paragraph.spec.ts

@@ -804,8 +804,10 @@ describe("Paragraph", () => {
                 ],
             });
             const fileMock = ({
-                DocumentRelationships: {
-                    createRelationship: () => ({}),
+                Document: {
+                    Relationships: {
+                        createRelationship: () => ({}),
+                    },
                 },
             } as unknown) as File;
             paragraph.prepForXml(fileMock);

src/file/paragraph/paragraph.ts

@@ -79,7 +79,7 @@ export class Paragraph extends XmlComponent {
             if (element instanceof ExternalHyperlink) {
                 const index = this.root.indexOf(element);
                 const concreteHyperlink = new ConcreteHyperlink(element.options.child, shortid.generate().toLowerCase());
-                file.DocumentRelationships.createRelationship(
+                file.Document.Relationships.createRelationship(
                     concreteHyperlink.linkId,
                     "http://schemas.openxmlformats.org/officeDocument/2006/relationships/hyperlink",
                     element.options.link,