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/crop.html

@@ -30,6 +30,7 @@
               </div>
             </div>
           </div>
+          <script type="module" th:src="@{'/pdfjs-legacy/pdf.mjs'}"></script>
           <script>
             let pdfCanvas  = document.getElementById('crop-pdf-canvas');
             let overlayCanvas = document.getElementById('overlayCanvas');