add support to close items
add support to close items

for that we add a checkbox that is only enabled if the item is not
closed and on click we call the tudu.item/close mutator with the id we
want to close and we tell transact that :tudu/items will change.

we define the mutator tudu.item/close to assoc the field :state of the
todo item for the given id to :close

marianoguerra-atik/tudu-v1