Enforce updating of fields when opening a word document

This commit sets `XWPFDocument#enforceUpdateFields` to true so
that users are asked whether they want to update the references
in the document on first opening it.

src/main/java/com/docutools/jocument/impl/word/WordDocumentImpl.java

@@ -41,6 +41,8 @@ protected Path generate() throws IOException {
       logger.debug("Retrieved all body elements, starting WordGenerator");
       WordGenerator.apply(resolver, bodyElements, options);
 
+      document.enforceUpdateFields();
+
       try (OutputStream os = Files.newOutputStream(file)) {
         logger.info("Writing document to {}", os);
         document.write(os);