Update pdf-view.css to enable auto cell size

A new line is added to the .pdf-view class in the pdf-view.css. This change has been made to allow automatic sizing of the cells on the UI by setting the -fx-cell-size to -1. This will enhance the view by adjusting the cell sizes based on the content.

pdfviewfx/src/main/resources/com/dlsc/pdfviewfx/pdf-view.css

@@ -45,6 +45,7 @@
     -fx-background: rgb(245, 245, 245);
     -fx-background-color: -fx-background;
     -fx-padding: 20 20 10 10;
+    -fx-cell-size: -1;
 }
 
 .pdf-view .thumbnail-list-view .list-cell:odd,