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/adjust-contrast.html

@@ -53,7 +53,8 @@
 
               </div>
               </form>
-
+              <script type="module" th:src="@{'/pdfjs-legacy/pdf.mjs'}"></script>
+              <script th:src="@{'/js/thirdParty/pdf-lib.min.js'}"></script>
               <script>
                 var canvas = document.getElementById('contrast-pdf-canvas');
                 var context = canvas.getContext('2d');