Load pdf libs when needed (#1902)

* feat: only load pdf-lib when its used

* feat: only load pdfjs when its used

src/main/resources/templates/misc/compare.html

@@ -79,6 +79,7 @@
                   <div id="result2" class="result-column"></div>
                 </div>
               </div>
+              <script type="module" th:src="@{'/pdfjs-legacy/pdf.mjs'}"></script>
               <script>
                 // get the elements
                 var result1 = document.getElementById('result1');