add settings option to add trackRevisions

src/file/settings/track-revisions.spec.ts

@@ -0,0 +1,16 @@
+import { expect } from "chai";
+import { Formatter } from "export/formatter";
+import { TrackRevisions } from "file/settings/track-revisions";
+
+import { EMPTY_OBJECT } from "file/xml-components";
+
+describe("TrackRevisions", () => {
+    describe("#constructor", () => {
+        it("creates an initially empty property object", () => {
+            const trackRevisions = new TrackRevisions();
+
+            const tree = new Formatter().format(trackRevisions);
+            expect(tree).to.deep.equal({ "w:trackRevisions": EMPTY_OBJECT });
+        });
+    });
+});