Add comments to the JavaFX codebase

src/main/java/org/nwapw/abacus/fx/CopyableCell.java

@@ -6,8 +6,17 @@ import javafx.scene.input.MouseEvent;
 import java.awt.*;
 import java.awt.datatransfer.StringSelection;
 
+/**
+ * A cell that copies its value to the clipboard
+ * when double clicked.
+ * @param <S> The type of the table view generic type.
+ * @param <T> The type of the value contained in the cell.
+ */
 public class CopyableCell<S, T> extends TableCell<S, T> {
 
+    /**
+     * Creates a new copyable cell.
+     */
     public CopyableCell(){
         addEventFilter(MouseEvent.MOUSE_CLICKED, event -> {
             if(event.getClickCount() == 2){