paragraph: add support for page break before format property (#7)

src/file/paragraph/formatting/page-break.spec.ts

@@ -1,7 +1,7 @@
 import { assert } from "chai";
 
 import { Utility } from "../../../tests/utility";
-import { PageBreak } from "./page-break";
+import { PageBreak, PageBreakBefore } from "./page-break";
 
 describe("PageBreak", () => {
     let pageBreak: PageBreak;
@@ -30,3 +30,11 @@ describe("PageBreak", () => {
         });
     });
 });
+
+describe("PageBreakBefore", () => {
+    it("should create page break before", () => {
+        const pageBreakBefore = new PageBreakBefore();
+        const newJson = Utility.jsonify(pageBreakBefore);
+        assert.equal(newJson.rootKey, "w:pageBreakBefore");
+    });
+});