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.ts

@@ -0,0 +1,25 @@
+import { SpaceType } from "file/space-type";
+import { XmlAttributeComponent, XmlComponent } from "file/xml-components";
+import { IPageRefOptions } from "./pageref-properties";
+
+class TextAttributes extends XmlAttributeComponent<{ readonly space: SpaceType }> {
+    protected readonly xmlKeys = { space: "xml:space" };
+}
+
+export class PageRefFieldInstruction extends XmlComponent {
+    constructor(bookmarkId: string, options: IPageRefOptions = {}) {
+        super("w:instrText");
+        this.root.push(new TextAttributes({ space: SpaceType.PRESERVE }));
+
+        let instruction = `PAGEREF ${bookmarkId}`;
+
+        if (options.hyperlink) {
+            instruction = `${instruction} \\h`;
+        }
+        if (options.useRelativePosition) {
+            instruction = `${instruction} \\p`;
+        }
+
+        this.root.push(instruction);
+    }
+}