Add the pageref element

This instruction is useful if you want to get the number of the page
containing a specific bookmark.

src/file/paragraph/links/pageref-field-instruction.spec.ts

@@ -0,0 +1,24 @@
+import { expect } from "chai";
+
+import { Formatter } from "export/formatter";
+import { PageRefFieldInstruction } from "./pageref-field-instruction";
+
+describe("PageRef field instruction", () => {
+    describe("#constructor()", () => {
+        it("should construct a pageref field instruction without options", () => {
+            const instruction = new PageRefFieldInstruction("anchor");
+            const tree = new Formatter().format(instruction);
+
+            expect(tree).to.be.deep.equal({
+                "w:instrText": [
+                    {
+                        _attr: {
+                            "xml:space": "preserve",
+                        },
+                    },
+                    "PAGEREF anchor",
+                ],
+            });
+        });
+    });
+});