In some cases, form items go together with a checkbox which can be used to disable the item.
An example for such an item is the line edit in the first row of the screenlocker kcm.
Here, a checkbox is prepended to the line edit's label.
In Kirigami, there is (afaik) no way to add a widget to a FormLayout item's buddyComponent.
This patch adds an optional checkbox to the buddyComponent.
A place where I would like to use this is the fonts kcm: https://phabricator.kde.org/T7927#132277