fix(checkbox): show pointer on css only linked labels

CSS Only checkboxes without Javascript which have linked labels (<label for="id">) to be (un) checked by clicking on its label did not have any pointer indicators and text was selected on dragging.

src/definitions/modules/checkbox.less

@@ -266,6 +266,7 @@
 }
 
 /* Selectable Label */
+.ui.checkbox input + label[for],
 .ui.checkbox input.hidden + label {
   cursor: pointer;
   user-select: none;