add support for checklist items in todos

[danvac]

I am trying to add checklist items under todos.

habitipy todos add todo item --check check1 --check check2

and I had also updated todo list to show checks.

$ habitipy todos add todo item --check check1 --check check2
Added todo 'todo item' with priority 1
 1. ▄✖ todo item 0/2

list will print checklist items only with --full defined

$ habitipy todos --full
 1. ▄✖ test 0/2
       - 1
       - 2